# Photon 2015

Asia/Novosibirsk
,
Description

### International Conference on the Structure and the Interactions of the Photon including the 21th International Workshop on Photon-Photon Collisions and the International Workshop on High Energy Photon Colliders

The International Conference PHOTON 2015 will be held at Budker Institute of Nuclear Physics (BINP), Siberian Branch of Russian Academy of Science, Novosibirsk, Russia, from 15 to 19 June, 2015.

This conference is a part of the series initiated in 1973 in Paris, as an International Colloquium on Photon-Photon Collisions at Electron-Positron Storage Rings. The latest Photon conferences took place in Paris (2013), Spa(2011), Hamburg(2009), Paris (2007), Warsaw (2005) and in Frascati (2003). At the conference, recent progress in understanding photon-photon and photon-proton processes will be presented. In addition, recent results on astrophysics and other related topics will be discussed.

Participants
• Albert De Roeck
• Aleksey Berdyugin
• Alexander Barnyakov
• Alexander Bobrov
• Alexander Bondar
• Alexander Kuzmin
• Alexander Potylitsyn
• Alexandr Blinov
• Alexandr Popov
• Alexei Safonov
• Alexey Kiselev
• Alexey Onuchin
• Anastasiya Kuzmenko
• Anatoly Vorobiov
• Andrea Ferrero
• Andreas Nyffeler
• Andrey Grabovsky
• Andrey Sokolov
• Anna Vinokurova
• Anton Osipov
• Artem Ryzhenenkov
• Attila Krasznahorkay
• Aurelien Martens
• Babette Doebrich
• Benedikt Kloss
• Boris Shwartz
• Dave besson
• Dieter H.H. Hoffmann
• Dmitriy Korda
• Dmitry Ivanov
• Dmitry Matvienko
• Dmitry Shemyakin
• Ekaterina Avdeeva
• Elena Pakhtusova
• Evgenii Baldin
• Evgeniy Kravchenko
• Evgeny Solodov
• Fedor Ignatov
• Felix Karbstein
• Francesca Curciarello
• Frederic Kapusta
• Gelb Kotkin
• Georgii Shestakov
• Giuseppe Mandaglio
• Gongjun Tao
• Graziano Venanzoni
• Guido Zavattini
• Hermann Kolanoski
• Hiroyuki Sagawa
• Ilkka Helenius
• Ilya Ginzburg
• Ivan Kuyanov
• Ivan Logashenko
• Ivan Ovtin
• Jan Friedrich
• Junquan Tao
• Leandro Cieri
• Marc Escalier
• Marc KNECHT
• Maria Krawczyk
• Maurice Claude Benayoun
• Maxim Kuzin
• Mikhail Egorov
• Nikolay Achasov
• Nikolay Gabyshev
• Olga Lukina
• Pablo Sanchez Puertas
• Patricia Rebello Teles
• Peter Krachkov
• Peter Lukin
• Rainer Schicker
• Ravel Akhmetshin
• Renaud Boussarie
• Roman Gerasimov
• Roman Lee
• Savely Karshenboim
• Sergey Kononov
• Sergey Serednyakov
• Sergey Strokov
• Shulan Zhang
• Simon Eidelman
• steven prohira
• Svenja Urban
• Tatyana Dimova
• Timofey Uglov
• Ulrike Schnoor
• Uri Karshon
• Uwe Schneekloth
• Valeriy Serbo
• Valery Tayursky
• Valery Telnov
• Vasiliy Shebalin
• Vassili Kazanin
• Victor Chernyak
• Victor Paulo Barros Gonçalves
• Victor Zhilich
• Vitaly Vorobyev
• Yohei Yamaguchi
• Yuri Skovpen
• Yuriy Tikhonov
• Yury Rogovsky
Support
• Monday, 15 June
• 08:00 09:00
Registration (bus from hotel at 9:10) 1h
• 09:00 09:10
Welcome by Prof. Alexander SKRINSKY, Dr. Pavel LOGATCHOV 10m
• 09:10 11:55
Higgs and photons, electroweak and new physics
Convener: Prof. Uri Karshon (Weizmann Institute)
• 09:10
Higgs studies, present and future 25m
.
Speaker: Prof. Albert De Roeck (CERN)
• 09:35
Highlights from the ATLAS experiment 30m
ATLAS is one of the general purpose experiments at the Large Hadron Collider (LHC), beginning its data taking in 2009. The Run 1 data taking of ATLAS ran from 2009 until the beginning of 2013, collecting ~25 fb-1 of p-p collision data. After LHC's Long Shutdown 1, ATLAS is restarting its Run 2 data taking operations in just these weeks. In this talk I will give an overview of the most recent results of the experiment, using the full Run 1 (7 and 8 TeV) datasets. Including the recent Higgs combination results, results from searches for beyond the Standard Model processes, and the most recent precision measurements.
Speaker: Dr Attila Krasznahorkay (CERN)
• 10:05
Highlights from the CMS experiment 30m
.
Speaker: Prof. Alexei Safonov (Texas A&M University)
• 10:35
Coffee 30m
• 11:05
Latest results on Higgs final-states with photons in ATLAS 25m
A measurement of the Higgs boson property with photon final states in proton-proton collisions with the ATLAS detector at the LHC is presented. The results are based on the data samples corresponds to integrated luminosities of 4.7 fb$^{-1}$ at $\sqrt{s}=7$ TeV in 2011 and 20.3 fb$^{-1}$ at $\sqrt{s}=8$ TeV in 2012. From a narrow resonance in diphoton mass spectrum, the mass of the Higgs boson is measured to be $m_{H} = 125.98 \pm 0.50$ GeV. The measured signal yield, which is a cross section times branching fraction normalised to the Standard Model expectation, is $1.17 \pm 0.27$. These results are based on improvements of photon energy reconstruction with the ATLAS detector.
Speaker: Dr Yohei Yamaguchi (Osaka University)
• 11:30
Latest results on Higgs final-states with photons in CMS 25m
Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are presented. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the LHC running periods in years 2011 and 2012. The data samples correspond to integrated luminosities of 5.1 $fb^{-1}$ at centre-of-mass energy 7 TeV and 19.7 $fb^{-1}$ at 8 TeV. A clear signal is observed in the diphoton channel at a mass close to 125 GeVwith a local significance of 5.7 $\sigma$, where a significance of 5.2 $\sigma$ is expected for the standard model Higgs boson. The mass is measured to be 124.70 $\pm$ 0.31 (stat.) $\pm$ 0.15 (syst.) GeV, and the best-fit signal strength relative to the standard model prediction is 1.14 $\pm$ 0.21 (stat.) +0.09-0.05 (syst.) +0.13-0.09 (theo.). Additional measurements including the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models, are also presented.
Speaker: Mr Junquan Tao (Institute of High Energy Physics, Chinese Academy of Sciences)
• 12:00 12:10
Group photo 10m
• 12:10 13:30
Lunch 1h 20m
• 13:30 16:55
Higgs and photons, electroweak and new physics
Convener: Prof. Albert De Roeck (CERN)
• 13:30
Latest results on anomalous gauge couplings in ATLAS 25m
New physics in the electroweak sector can be described in a model-independent way via anomalous gauge couplings. Measurements of these parameters allow for the exclusion or discovery of contributions beyond the Standard Model. Experimentally, the electroweak gauge couplings are accessible via di-boson production, vector boson production through vector boson fusion, vector boson scattering, and triple boson production. The talk describes measurements of various channels of di-boson production, vector boson fusion, vector boson scattering, and triple boson produciton with the ATLAS detector and the derived limits on anomalous triple and quartic gauge couplings. All measurements show good agreement with the Standard Model.
Speaker: Dr Ulrike Schnoor (IKTP TU Dresden)
• 13:55
Latest results on anomalous gauge couplings in CMS 25m
The talk covers CMS results for the limits on anomalous triple and quartic gauge couplings based on data collected with LHC center-of-mass collision energy of sqrt(s)=7 TeV and sqrt(s)=8 TeV with corresponding integrated luminosities of 5 fb^-1 and 19.5 fb^-1 respectively. The limits are derived from the analysis of Vgamma, WV, WVgamma production. All results are consistent with the Standard Model predictions.
Speaker: Mrs Ekaterina Avdeeva (University of Nebraska - Lincoln)
• 14:20
Results on isolated photon, photon+jet and diphoton production in ATLAS 25m
Isolated photons are a rich probe to explore various physics subjects at LHC. After presenting the strategy to identify the photons and measure the background, the various results of measurements based on photons are reviewed, using collisions based either on protons or lead ions.
Speaker: Dr Marc Escalier (LAL)
• 14:45
Coffee 30m
• 15:15
Diphoton production at NNLO at the LHC 20m
In this talk we present the diphoton production at NNLO in pQCD. We show the comparison of the NNLO QCD prediction with recent measurements from the LHC. Also we show a study about the isolation prescription and we present the first results on transverse momentum resummation at NNLL+NLO accuracy.
Speaker: Dr Leandro Cieri (Postdoc)
• 15:35
Higgs and photons 20m
In my talk I will describe role of photons in testing scalar sector of the SM and its extensions. In particular constraints on the Inert Doublet Model will be presented in the light of the recent LHC results on gamma gamma decay of the 125 GeV Higgs. They lead to strong limits on Dark Matter mass and its coupling to the Higgs particle.
Speaker: Prof. Maria Krawczyk (University of Warsaw)
• 15:55
Two-photon Higgs width and triple Higgs coupling in 2HDM in SM-like scenario 20m
Within 2HDM deviations of the two-photon Higgs width and the value of triple Higgs coupling from their values in the SM are connected to each other. If SM-like scenario for observed Higgs boson is realized, mentioned deviations can be visible either simultaneously or inaccessible for observation at the LHC. Photon Collider can help in the checking up this connection
Speaker: Prof. Ilya Ginzburg (Sobolev Inst. of Mathematics SB RAS and Novosibirsk State University)
• 16:15
New physics possibilities in photon-induced interactions at the LHC 20m
In the last years the Large Hadron Collider (LHC) at CERN has collected a large amount of data considering $pp$, $pPb$ and $PbPb$ collisions, which is allowing to probe the Standard Model in a new kinematical range. In this talk I will show that the LHC can also be considered as a photon collider, which allows to study several aspects of the hadronic physics by the analysis of photon induced interactions in hadronic collisions. The basic idea is that in these interactions the total cross section for a given process can be factorized in terms of the equivalent flux of photons into the hadron projectile and the photon-photon or photon-target production cross section. The main advantages of using hadron - hadron collisions for studying photon induced interactions are the high equivalent photon energies and luminosities that can be achieved at existing accelerators. I review recent results which demonstrate that photon induced interactions at LHC can be used to study the QCD dynamics at high energies, the Odderon, Meson properties, Charmoniumlike Exotic states, and Beyond Standard Model Physics.
Speaker: Prof. Victor Paulo Goncalves (UFPel/Brazil)
• 16:35
Searches for Dark Forces at e+e- Colliders 20m
A new force beyond the Standard Model (SM) is postulated by several SM extensions and its search is well motivated by many puzzling astrophysical effects recently observed in cosmic ray spectra. The mediator of this “dark force” should be a new neutral light vector gauge boson, known as $U$ boson, weakly coupled to ordinary particles and associated to an abelian gauge symmetry. Moreover, the new symmetry should be broken by a Higgs-like mechanism thus suggesting existence of an additional scalar particle, the dark Higgs ($h^{\prime}$). In principle, the dark photon would be produced in any process in which a photon is involved but with a rate strongly suppressed by the small coupling. In this respect, high intensity flavor factories are an ideal place to investigate dark forces due to high statistics, good knowledge of backgrounds and clear event topology. At $e^+e^-$ colliders, dark forces can be probed by exploiting radiative meson decays, dark Higgsstrahlung and Initial State Radiation (ISR) processes. By assuming prompt visible $U$ decays, the KLOE-2 experiment performed five searches by investigating the Dalitz decay $\phi \to \eta U,~U \to e^+e^-$, tagging the $\eta$ meson by its $\pi^+ \pi^- \pi^0$ and $3\pi^0$ decays and radiative $e^+e^- \to U \gamma$ events with $U \to l^+l^-~(l = e, \mu)$. KLOE-2 searched also for the dark Higgsstrahlung process by assuming the invisible scenario, where $m(U) > m(h^{\prime})$ and the dark Higgs escapes detection showing up a missing energy. Complementary searches of dark Higgsstrahlung have been also performed in the BaBar and Belle experiments by considering the visible scenario $m(U) < m(h^{\prime})$. BaBar set also a stringent combined limit on $U$ coupling by using the ISR process $e^+e^- \to U \gamma$ with $U$ decaying into leptons. Focus will be made on details of setting limits on the coupling strength between the photon and the dark photon in the KLOE-2, BaBar and Belle experiments.
Speaker: Dr Francesca Curciarello (Dipartimento di Fisica e di Scienze della Terra, Universita di Messina, INFN Sezione Catania, Messina, Italy, Novosibirsk State University, Novosibirsk, Russia)
• 17:00 19:30
Welcome party (bus to hotel at 20:30) 2h 30m
• Tuesday, 16 June
• 08:00 12:00
Two-photon physics history
Convener: Prof. Maria Krawczyk (University of Warsaw)
• 08:00
First evidence of two-photon production of e+e- pairs at VEPP-2 in Novosibirsk 25m
.
Speaker: Dr Elena Pakhtusova (Budker INP)
• 08:25
Two Photon Physics in France : a tribute to Paul Kessler 25m
The interest in photon-photon collisions in the 70's led to the 1973 Conference. A brief historical review will emphasize the rôle of Paul Kessler and his colleagues.
Speaker: Dr Frederic Kapusta (LPNHE Paris)
• 08:50
Towards to history of two photon physics. 25m
In this report I present personal view for history of two-photon physics
Speaker: Prof. Ilya Ginzburg (Sobolev Inst. of Mathematics SB RAS and Novosibirsk State University)
• 09:15
First evidence of two-photon production of C+ resonances at SPEAR with detector MARK-2 20m
In this talk I tell on first observation of C+ resonances (eta-prime and f2) in two photon collisions at e+e- storage
Speaker: Prof. Valery Telnov (BINP, Novosibirsk Univ.)
• 09:35
Coffee 30m
• 10:05
A historical retrospect of Two-Photon Physics in the 1980ies at DORIS, SPEAR, PETRA and PEP 40m
The major developments and achievements in two-photon physics obtained at the electron-positron colliders DORIS, SPEAR, PETRA and PEP are reviewed. These machines allowed for the first time detailed studies of hadron production in high-energy photon-photon collisions. With the advent of sufficiently high energies at PETRA and PEP the studies of resonant two-photon couplings were complemented by investigations of the perturbative QCD regime leading to the first observations of jet production and to measurements of the hadronic structure of the photon.
Speaker: Prof. Hermann Kolanoski (Humboldt University/DESY)
• 10:45
Two-photon experiments with detector MD1 at VEPP-4 25m
Detector MD-1 worked at storage ring VEPP-4 in 1980-85. Its specific feature was a transverse magnetic field for better detection of two photon processes. Detection of both scattered electrons enabled to measure the total gamma-gamma cross section. Also some other two-photon processes have been studied with and without detection of the scattered electrons.
Speaker: Prof. Valery Telnov (BINP, Novosibirsk Univ.)
• 11:10
Two-photon experiments at CESR 25m
Speaker: Dr Dave Besson (University of Kansas)
• 11:35
Two-photon physics from TRISTAN 25m
As a part of the historical two-photon session, I summarize achievements from the three TRISTAN experiments, AMY, TOPAZ and VENUS. Results related to a confirmation of the "resolved-photon" processes, where the quark and gluon contents in a photon play a role, are highlight of the measurements.
Speaker: Dr Sadaharu Uehara (KEK, High Energy Accelerator Research Organization)
• 12:00 13:30
Lunch (+meeting of the Intern. Advisory Com.) 1h 30m
• 13:30 14:50
Two-photon physics history
Convener: Dr Maurice Benayoun (LPNHE Paris 6/Paris 7)
• 13:30
Birth of colliding beams in Europe, two-photon studies at Adone(remote) 25m
.
Speaker: Dr Giulia Pancheri (INFN)
• 13:55
Two-photon physics from LEP 30m
Speaker: Dr Frederic Kapusta (LPNHE Paris)
• 14:25
An idea of high energy γγ, γe colliders based on one pass e+e- linear colliders. 25m
The gamma-gamma luminosity in collisions of virtual photons at e+e- storage rings is much lower than that in e+e- collisions and the spectrum is rather soft. In 1980 we have noticed that at high energy linear colliders beams are used only ones which makes possible to convert electrons to high energy photons using Compton scattering of laser photons and thus to obtain real gamma-gamma collisions with energies and luminosities similar to e+e- collisions. Such high energy gamma-gamma (gamma-electron) colliders are technically feasible now and are considered as a natural option in all e+e- linear collider projects
Speaker: Prof. Valery Telnov (BINP, Novosibirsk Univ.)
• 14:50 15:20
Coffee 30m
• 15:20 16:35
Photons in astroparticle physics
Convener: Dr Maurice Benayoun (LPNHE Paris 6/Paris 7)
• 15:20
Radiowave detection of UHECR in Antarctica 25m
The recent detection of ultra-high energy neutrinos has provided new impetus for similar experiments seeking measurement of neutrinos, photons and other cosmic rays at the highest energy regime. We will discuss recent attempts to measure the GZK neutrino flux via radio techniques, and prospects and plans for the future.
Speaker: Dr Dave Besson (MEPhI)
• 15:45
Recent results from the Telescope Array - studies of ultra-high energy cosmic rays and the prospect - 25m
The Telescope Array (TA) experiment aims at studying the nature and origin of Ultra-high Energy Cosmic Rays (UHECRs) with energies up to around 10^20 eV. It is located in Utah, USA, and is composed of a ground array of 507 scintillator detectors covering 700 square kilometers and three air fluorescence telescope stations overlooking the array from the periphery. Here I present the recent results of the measurements of UHECR spectrum, anisotropy and composition from TA including the preliminary results at lower energies down to 10^15.6 eV from the TA Low-energy Extension (TALE). And the TA extension plans are also presented.
Speaker: Dr Hiroyuki Sagawa (Institute for Cosmic Ray Research, the University of Tokyo)
• 16:10
Radio Detection of Ultra High Energy Cosmic Rays with the Telescope Array Radar Remote Stations 25m
The Telescope Array Radar (TARA) Remote Station is a novel, autonomous, radio-based detector for Ultra High Energy Cosmic Rays (UHECR). Our bi-static radar approach utilizes the ionized core of an UHECR shower as a reflector for a continuous wave (cw) signal. By analyzing this reflected signal, we can reconstruct the UHECR event. Our detection scheme allows for the coverage of a very large area with a minimum of apparatus, thus lowering the effective cost of UHECR detection, and raising the likelihood of seeing higher energy UHECR per increase in event area.
Speaker: Mr Steven Prohira (University Of Kansas)
• 16:35 17:35
Excursion to BINP facilities 1h
• Wednesday, 17 June
• 08:00 11:30
Muon g-2
Convener: Dr Marc Knecht (CNRS - CPT Marseille)
• 08:00
Theoretical status of the muon g-2 25m
The anomalous magnetic moment of the muon is sensitive to loop contributions from all sectors of the Standard Model and, potentially, to virtual particles of New Physics. In fact, since many years there is an intriguing discrepancy of 3-4 standard deviations between experiment and theory. However, the hadronic uncertainties from vacuum polarization and light-by-light scattering dominate the theory error and make it difficult to interpret this deviation as a clear sign of New Physics. We present some recent developments in the theory of the muon g-2 and give an update on the current status. We end with an outlook on how to better control the hadronic uncertainties, in order to fully profit from planned future muon g-2 experiments to test the Standard Model and to constrain models of New Physics.
Speaker: Dr Andreas Nyffeler (Institute of Nuclear Physics, University of Mainz, Germany)
• 08:25
Mesurement of the π+π- cross section at BESIII 20m
Precise hadronic cross section measurements are an important input for the standard model prediction of $(g-2)_\mu$. Especially, the most important hadronic cross section as input for $(g-2)\mu$, $\sigma_{\pi\pi} = \sigma(e^+e^-\rightarrow \pi^+\pi^-)$, has been measured over decades with ever increasing accuracy at accelerators in Novosibirsk, Orsay, and Frascati. More recently, the two most accurate measurements have been obtained by the KLOE collaboration in Frascati, and the BABAR collaboration at SLAC. Both experiments claim an accuracy of better than 1% in the energy range below 1 GeV, in which the $\rho(770)$ resonance is dominating the hadronic cross section. However, a discrepancy of approximately 3% on the peak of the $\rho(770)$ resonance is observed. The discrepancy is even increasing towards higher energies. Unfortunately, this discrepancy is limiting our current knowledge of $a_\mu \equiv (g-2)\mu/2$, which is a famous precision observable of the Standard Model (SM). The accuracy of the SM prediction of $(g-2)\mu$, is entirely limited by the knowledge of the hadronic vacuum polarization contribution, which is obtained in a dispersive framework by using experimental R-ratio data on $\sigma(e^+e^-\rightarrow \rm hadrons)$. The cross section $\sigma_{\pi\pi}$ contributes more than 70% to this dispersion relation and, hence, is the by far most important exclusive hadronic channel of the total hadronic cross section. Currently, a discrepancy of 3.6 standard deviations is found between the direct measurement of $a_\mu$ and its SM prediction. However, the discrepancy reduces to 2.4$\sigma$, when only BABAR data is used as input to the dispersion relation, which shows the need for a new measurement. In this talk, we are presenting a new measurement of the cross section $\sigma_{\pi\pi}$ at the BESIII experiment in Beijing.
Speaker: Mr Benedikt Kloss (Institute for Nuclear Physics Mainz)
• 08:45
Low-energy hadronic cross sections measurements at BaBar, and implication for the g-2 of the muon 20m
The BABAR Collaboration has an intensive program  studying hadronic cross sections at low-energy e+e- annihilations, accessible via initial-state radiation. These measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. We report here the results of recent studies on a number of final states, as e+e- -> K+K-,  e+e- -> K_S K_L, and e+e- -> K_S K+ pi- pi0.
Speaker: Dr Eugeny Solodov (BINP)
• 09:05
Results and prospects on hadronic cross section and γγ physics at KLOE/KLOE-2 20m
The KLOE experiment was the first to exploit Initial State Radiation (ISR) processes to obtain the $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ cross section below 1 GeV. Three measurements have been published with small angle photon in the initial state: normalized using luminosity from Bhabha in 2005 and 2008 and using $\pi\pi\gamma / \mu\mu\gamma$ ratio in 2014. An independent measurement with the large angle photon normalized to Bhabha has been published in 2011. These measurements are in good agreement, showing a good consistency among different analyses. The Gounaris-Sakurai fit of the pion form factor of the combined KLOE measurements will be also discussed. We also present the $\gamma\gamma$ physics project of KLOE-2 experiment, made possible after the recent KLOE upgrade with new small angle tagging detectors along the DAFNE beam line. The new detectors combined with KLOE apparatus allow to measure the $\pi^0\rightarrow\gamma\gamma$ decay and $\gamma^*\gamma\rightarrow\pi^0$ transition form factor. These measurements provide constraints to the models used to calculate the hadronic light-by-light contribution to the muon anomaly.
Speaker: Dr Giuseppe Mandaglio (Dipartimento di Fisica e di Scienze della Terra)
• 09:25
Recent results from VEPP-2000 20m
Since 2010 two detectors, CMD-3 and SND, have been collecting statistics at the electron-positron collider VEPP-2000. Until first technical stop in 2013, the integrated luminosity exceeded 60 pb$^{-1}$ for each detector in the wide c.m. energy range from 0.32 up to 2 GeV. The current status of analysis as well as recent results are reported.
Speaker: Dr Vassili Kazanin (BINP)
• 09:45
Coffee 30m
• 10:15
Measuring the Leading order hadronic contributon to g-2 in the space like region 25m
I will present a novel approach (see http://arxiv.org/abs/1504.02228 [1] Phys. Lett. B46 (2015) 325-329), to determine the leading hadronic corrections to the muon g-2. It consists in a measurement of the effective electromagnetic coupling in the space-like region extracted from Bhabha scattering data. This method can result in an alternative determination potentially competitive with the dispersive approach via time-like data. I will discuss its possible application at low energy e+e- machines like DAFNE, VEPP2000, BEPCII and SuperKEKB.
Speaker: Dr Graziano Venanzoni (LNF-INFN)
• 10:40
Pseudoscalar-exchange contribution to g-2 from rational approximants 25m
Padé Approximants have been used to describe the light pseudoscalars transition form factors (TFFs) in the space-like region. Once the low energy parameters are determined from a fit to data, they provide a systematic and model-independent tool for describing the TFFs. We discuss their generalization to the bivariate case, which allows a systematic description for the double-virtual TFF. This is of utmost relevance for the Light-by-Light contribution to g-2. Lacking double-virtual data, we discuss expectations and its connection with pseudoscalar decays into lepton-pairs.
Speaker: Mr Pablo Sanchez Puertas (Johannes Gutenberg University, Mainz)
• 11:05
VMD/HLS Approach to the muon (g-2) : A solution to the tau-e+e- puzzle 25m
The Hidden Local Symmetry (HLS) Model provides a framework able to encompass several physical processes and give a unfied description of these in an energy range extending up to the $\phi$ mass. However, in order to account precisely for experimental data, it should be supplied with several symmetry breaking schemes. Among these, an energy dependent mixing mechanism of the vector mesons ($\rho^0-\omega-\phi$) is generated via loop effects and allows to define an effective broken HLS (BHLS) model. Within this framework the $e^+ e^-$ annihilations to $\pi^+\pi^-$, $\pi^0 \gamma$, $\eta \gamma$, $\pi^+\pi^- \pi^0$, $K^+ K^-$, $K_L K_S$ and the dipion spectrum in the decay $\tau^\pm \rightarrow \pi^\pm \pi^0 \nu$ are $simultaneously$ accounted for with the same set of model parameters. These are derived from global fits in procedures involving all existing data samples covering the channels within the BHLS scope. The muon HVP's derived from fits performed with and without the $\tau$ dipion spectra are found consistent with each other. Therefore, within the broken HLS approach, one does not observe any clear mismatch between the $\tau$ and $e^+e^-$ physics properties.
Speaker: Dr Maurice Benayoun (LPNHE Paris 6/Paris 7)
• 11:30 11:55
Low-energy photon experiments, vacuum polarization and light-by-light scattering
Convener: Dr Rainer Schicker (Phys. Inst., Uni Heidelberg)
• 11:30
Results and Prospect of measuring vacuum magnetic birefringence with PVLAS 25m
A new highly sensitive ellipsometer is now running at the Department of Physics and INFN of Ferrara, Italy. The apparatus has been designed to detect very small magnetically induced birefringences with the ultimate goal of measuring vacuum magnetic birefringence. This challenging goal is not yet achievable due to excess noise which is under study. Nonetheless new limits on vacuum magnetic birefringence have been recently set and measurements are still underway. Taking advantage of the cavity intrinsic birefringence, our ellipticity limit can also be used to set a dichroism limit. From these two values we set model independent limits on the coupling constant of axion like particles to two photons.
Speaker: Prof. Zavattini Guido (University of Ferrara and INFN-Ferrara)
• 11:55 13:30
Lunch 1h 35m
• 13:30 14:45
Low-energy photon experiments, vacuum polarization and light-by-light scattering
Convener: Dr Rainer Schicker (Phys. Inst., Uni Heidelberg)
• 13:30
Photons as signature for dark matter and dark energy: The Cast experiment at CERN 25m
The CAST experiment is designed to search for solar axions which are produced in the interior of the sun via the Primakoff effect. The central part of the experiment, the helioscope is an LHC prototype magnet that has attached different types of sensitive detectors for x-rays in the regime of 1-10 keV. The experiment has been taking data since 2003 and provided the most restrictive limits on the axion-photon coupling in a broad mass range. Beyond 0,02eV/c**2 the mass the sensitivity is degraded due to coherence loss. In order to restore coherence, the magnet was filled with a buffer gas providing an effective mass to the photon. By changing the pressure of the buffer gas in steps, CAST did scan the range of axion mass values from 0.02eV to 1.18eV. CAST has set the strongest limit yet on Axion-photon coupling across a wide range of Axion masses (i.e., any rest mass below 1.18eV), surpassing astrophysical limits for the first time. An overview of the total data set and data analysis will be presented. The significant upgrades of CAST in 2014 allows first experiments to shed some light into the dark energy sector by searching for axions with its better performance due to a 2nd XRT, while continuing the search for solar chameleons in the sub-keV range. Proposals for the future include an International Axion Observatory (IAXO) as a 4th generation Axion Helioscope. This proposal is currently under review/approval by CERN SPS committee. IAXO follows the conceptual layout of an enhanced Axion Helioscope building on the expertise and the pioneering spirit of the CAST project.
Speaker: Prof. Dieter H.H. Hoffmann (Technische Universität Darmstadt)
• 13:55
Upcoming Hidden Photons Searches with ALPS-II and FUNK 25m
One of the simplest Standard Model extensions consists in a `Hidden Photon', coupled kinetically to the photon of the Standard Model. Such a particle could also constitute the Dark Matter. We highlight the most important theoretical and phenomenological aspects of ultra-light Hidden Photons and report on two upcoming experimental searches for such particles at DESY Hamburg (ALPS-II) and the KIT in Karlsruhe (FUNK).
Speaker: Dr Babette Doebrich (CERN)
• 14:20
All-optical probes of quantum vacuum nonlinearity 25m
We discuss various all-optical probes of quantum vacuum nonlinearity in strong electromagnetic fields. Our focus is on signatures of quantum vacuum nonlinearity in inhomogeneous field profiles, as attainable in the focal spots of realistic high-intensity laser experiments.
Speaker: Dr Felix Karbstein (Helmholtz Institut Jena)
• 14:45 15:15
Coffee 30m
• 15:30 21:00
Novosibirsk Philharmonic Theatre “History of Adolphe Sax”(Bus from BINP at 16:30) 5h 30m
• Thursday, 18 June
• 08:00 12:05
Resonances and exclusive processes
Conveners: Dr Jan Friedrich (TU München) , Prof. Nikolay Achasov (Sobolev Institute for Mathematics)
• 08:00
Light-quark mesons in two-photon processes at Belle 20m
We summarize results of light-quark meson studies for spectroscopy and their particle properties in two-photon processes at the Belle experiment. We report on dozens of different meson-state formation processes in the mass region, 0.9 - 2.6 GeV.
Speaker: Dr Sadaharu Uehara (KEK, High Energy Accelerator Research Organization)
• 08:20
The timelike electromagnetic form factors of proton and charged kaons at high energies 20m
The Initial State Radiation (ISR) method in the Babar experiment has been used to measure the timelike electromagnetic form factors at the momentum transfer from 9 to 42 GeV2 for protons and from 7 to 56 GeV2 for charged kaons. The obtained data show the tendency to approach the QCD asymptotic prediction for kaons and spacelike form factors values for proton.
Speaker: Prof. Sergey Serednyakov (Novosibrsk State University, BINP)
• 08:40
Photons interacting with Pions at COMPASS 20m
COMPASS is a multi-purpose experiment operated at CERN for investigations of the strong interaction from low to highest energy scales. At low energies, photon-pion interactions provide input for understanding the effective dynamics of strongly bound states of quarks and gluons, mostly prominently the recent measurement of the polarisability of the charged pion. At higher energies, the meson resonance spectrum comes into play. COMPASS investigates the coupling of photons to such resonances, which is described by their radiative widths.
Speaker: Dr Jan Friedrich (TU München)
• 09:00
COMPASS spectroscopy (remote) 20m
Speaker: Dr Boris Grube (TU, Munchen)
• 09:20
Exclusive processes at HERA 20m
The ratio of the exclusive electroproduction of psi(2S) and J/psi mesons has been measured at HERA. The results are sensitive to the wave functions of the vector mesons and are compared to predictions of QCD-inspired models of vector-meson production. Exclusive dijet production in diffractive deep inelastic scattering has been measured at HERA. Cross sections are presented as a function of $\beta$, the Bjorken variable defined with respect to the diffractive exchange and, in bins of $\beta$, as a function of $\phi$, the angle between the $\gamma^{\star}$--dijet plane and the $\gamma^{\star}$--e plane in the rest frame of the dijet final state. The results are compared to predictions from models which are based on different assumptions about the nature of the diffractive exchange. The first measurement of exclusive photoproduction of rho mesons associated with leading neutrons with the H1 detector at HERA is also presented. The data are interpreted in terms of two dominant contributions: diffractive proton dissociation channel and elastic production via virtual pion exchange. Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep inelastic scattering are presented as a function of the Feynman variable xF and of the centre-of-mass energy of the virtual photon-proton system, W. Predictions of deep inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.
Speaker: Dr Olga Lukina (SINP MSU)
• 09:40
Photon-hadron and photon-photon collisions in CMS (including data from p-p, p-A and A-A collisions) 20m
.
Speaker: Mrs Patricia Rebello Teles (Brazilian Center for Physics Research)
• 10:00
Coffee 30m
• 10:30
Photon-hadron and photon-photon collisions in ALICE 20m
Rainer Schicker for the ALICE collaboration Heavy-ion beams at high energy generate large photon fluxes which result in a variety of photon-hadron and photon-photon processes with large cross sections. The ALICE experiment at CERN is well suited to measure such reaction channels in the central barrel as well as in the forward muon spectrometer. The ALICE results from Run I of the LHC are presented, and an overview of our Run II plans is given.
Speaker: Dr Rainer Schicker (Phys. Inst., Uni Heidelberg)
• 10:50
Search for the eta' ->e+e- and eta -> e+e- decay at SND 15m
The decay eta' ->e+e- has been searched for at the VEPP-2000 e+e- collider with the SND detector using the reaction e+e- -> eta'. The following upper limits have been set at the 90% CL: Gamma(eta' -> e+e-) < 0.0020 eV and B(eta' -> e+e-) < 10^-8. Sensitivity of VEPP-2000 for measurement of the e+e- -> eta cross section has been studied.
Speaker: Dr Aleksey Berdyugin (Budker Institute of Nuclear Physics)
• 11:05
Photoproduction of π0π0 on proton and deuteron with the rescattering mechanism π+π- → π0π0 inclusion 15m
The model of coherent $\pi^0\pi^0$ mesons photoproduction on simplest nuclei of hydrogen and deiterium in the region $E_{\gamma}\le1.4$ GeV is presented. Two pion rescattering amplitude in process $\pi^+\pi^-\to\pi^0\pi^0$ is taken into account from phenomenological fit is accurately defined it in treshold region as well as up to 1100 MeV relative energy in $\pi\pi$ c.m. Strong dependence of the result on the rescattering amplitude is also discussed.
Speaker: Mr Mikhail Egorov (Tomsk Polytechnic University)
• 11:20
About the physics of the X(3872) resonance 15m
Enfant terrible of charmonium spectroscopy, the resonance X(3872), generated a stream of interpretations and ushered in a new exotic XYZ spectroscopy. In the meantime, many (if not all) characteristics of X(3872) are rather ambiguous. We construct spectra of decays of the resonance X(3872) with good analytical and unitary properties which allow to define the branching ratio of the X(3872) $\to D^{\star 0} \bar D^{0}$ + c.c. decay studying only one more decay, for example, the $X(3872)\to\pi+\pi- J/\psi(1S)$ decay. We next define the range of values of the coupling constant of the X(7872) resonance with the $D^{*0}\bar D^0$ chanel. We show also that our spectra are effective means of selection of models for the resonance X(3872). Contrary to almost standard opinion that the X(3872) resonance is the $D^{\star 0}\bar D^0+c.c.$ molecule or the $qc\bar q\bar c$ four-quark state, we prove the scenario where the X(3872) resonance is the $c\bar c = \chi_{c1}(2P)$ charmonium which "sits on" the $D^{*0}\bar D^0$ threshold. We explain the shift of the mass of the X(3872) resonance with respect to the prediction of a potential model for the mass of the $\chi_{c1}(2P)$ charmonium by the contribution of the virtual $D^*\bar D+c.c.$ intermediate states into the self energy of the X(3872) resonance. We suggest a physically clear program of experimental researches for verification of our assumption.
Speakers: Ms Elizaveta Rogozina (Novosibirsk State University) , Prof. Nikolay Achasov (Sobolev Institute for Mathematics)
• 11:35
To study isospin breaking decay η(1405)→f0(980)π0→3π 15m
We elucidate the possible mechanism of the isospin breaking decay $\eta(1405)\to f_0(980)\pi^0\to\pi^+\pi^-\pi^0$.
Speaker: Dr Georgii Shestakov (Institute for Mathematics, Novosibirsk)
• 11:50
Branching fractions of ψ(3770), ψ(4040), and Υ(10580) decays to light (non-DantiD, non-DsantiDs, and non-BantiB) hadrons 15m
Branching fractions of decays of heavy quarkonia $\psi(3770)$, $psi(4040)$, and $\Upsilon(10580)$ to the states $\pi^+\pi^-$, $K\bar K$, $\omega\pi^0$, $\omega\eta$, $\omega\eta^\prime$, $\rho\eta$, $\rho\eta^\prime$, $K^\ast\bar K+c.c.$, $\rho^+\rho^-$, $K^\ast\bar K^\ast$ etc are evaluated in the model of the Okubo - Zweig - Iizuka rule violation due to the real intermediate states of mesons with open open heavy flavors. The results are compared with existing experimental upper bounds.
Speaker: Dr Arkadii Kozhevnikov (S.L. Sobolev Institute for Mathematics)
• 12:05 13:30
Lunch 1h 25m
• 13:30 14:05
Resonances and exclusive processes
Convener: Dr Andreas Nyffeler (Institute of Nuclear Physics, University of Mainz, Germany)
• 13:30
To learn production of the scalar and tensor mesons in γγ∗(Q2)→ηπ0 reaction 15m
The prediction of the cross section $\sigma(\gamma\gamma^*(Q^2)\to \eta\pi^0)$ based on the simultaneous description of the Belle data on the $\gamma\gamma\to \eta\pi^0$ reaction and the KLOE data on the $\phi\to\eta\pi^0\gamma$ decay is presented.
Speaker: Dr Alexey Kiselev (Sobolev Institute for Mathematics)
• 13:45
Theoretical description of resonance production(remote) 20m
Speaker: Dr Christoph Hanhart (Julich)
• 14:05 14:40
Jets and inclusive reactions
Convener: Dr Andreas Nyffeler (Institute of Nuclear Physics, University of Mainz, Germany)
• 14:05
Combination of Measurements of Inclusive Deep Inelastic ep - Scattering Cross Sections and QCD Analysis of HERA data 20m
A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current ep scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in negative four-momentum-transfer squared, $Q_2$, and Bjorken $x$. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in alpha_s $(M_Z^2)$ = 0.1183 $\pm$ 0.0009(exp) $\pm$ 0.0005(model/parameterisation) $\pm$ 0.0012(hadronisation) +0.0037 -0.0030 (scale). An extraction $of xF_3(\gamma Z)$ and results on electroweak unification and scaling violations are also presented.
Speaker: Dr Uwe Schneekloth (DESY)
• 14:25
Monte Carlo event generation of photon-photon collisions at colliders 15m
In addition being interesting itself the photon-photon interactions will be an inevitable background for the future electron-positron colliders. Thus it is important to be able to simulate these collisions in a very good accuracy. In my talk I will present our ongoing work to implement the photon-photon collisions in PYTHIA8 event generator. First I will briefly describe how the partonic structure of the photon and differs from the structure of a proton. Then I will discuss about modifications of parton shower generation and beam remnant handling required to accommodate the photon beams into PYTHIA8. Finally I will present some preliminary results on particle production in photon-photon collisions and give an outlook about further developments.
Speaker: Dr Ilkka Helenius (Lund University)
• 14:40 15:05
Coffee 25m
• 15:05 15:45
Heavy flavor production
Convener: Dr Sadaharu Uehara (KEK, High Energy Accelerator Research Organization)
• 15:05
ISR Studies of Charmonium Region at Belle 20m
An overview of the Belle studies of the hadron production with initial state radiation is presented. The talk includes results on the D(\*)D(\*)bar cross-section measurement as well as the results on exotic charmonium-like states search.
Speaker: Dr Timofey Uglov (MIPT and ITEP)
• 15:25
Heavy flavour production at HERA 20m
The copious production of charm quarks at HERA has yielded a detailed understanding of QCD dynamics, the only measure of the charm contribution to the proton structure, as well as measurements of the charm mass and the fragmentation parameters of charmed hadrons. Although with smaller samples, measurements of beauty production also place constraints on the structure of the proton and allow a measurement of the beauty quark mass. Several measurements of heavy quark production using different decay modes, are presented, both new individual measurements from the H1 and ZEUS collaborations, as well as combined data. These provide a powerful vindication of the form of the gluon density in the proton derived from scaling violations of inclusive deep inelastic scattering data. QCD fits to the data lead to measurements of the charm and beauty masses and also provide precise predictions for e.g. W and Z production at the LHC. Additionally, fragmentation fractions to the ground state charm hadrons are compared to e+e- data and previous HERA results. The data have a precision similar to that of the e+e- data and support the hypothesis that fragmentation is independent of the production process.
Speaker: Prof. Uri Karshon (Weizmann Institute)
• 15:45 17:10
Small x, diffraction, and total cross sections
Convener: Dr Sadaharu Uehara (KEK, High Energy Accelerator Research Organization)
• 15:45
Low x evolution equation for quadrupole operator 15m
The NLO nonlinear evolution equation for quadrupole operator is presented in the coordinate space. The quasi-conformal evolution equation is presented for the composite quadrupole opertor.
Speaker: Dr Andrey Grabovsky (Budker Institute of Nuclear Physics)
• 16:00
Application of the shockwave formalism to diffractive processes 15m
The shockwave formalism gives us tools for calculations beyond the usual approximations (dipole model...). Using it , we calculate the impact factor for jet production in diffractive DIS and for jet broadening in pA collisions.
Speaker: Mr Renaud Boussarie (LPT Orsay)
• 16:15
Production of a forward J/Psi and a backward jet at LHC as a test of BFKL dynamics 15m
J/Psi mesons are copiously produced at LHC. Inspired by the Mueller Navelet jet studies which allows to distinguish between BFKL and DGLAP dynamics, we propose to consider the production of a forward J/Psi accompanied by a backward jet. We make a feasibility study and compute the leading order differential cross section for such events in the BFKL framework.
Speaker: Mr Renaud Boussarie (LPT Orsay)
• 16:30
Two-photon exchange in electron-proton scattering -the OLYMPUS experiment at DESY 20m
The OLYMPUS experiment will measure the two-photon exchange amplitude in the elastic electron-proton scattering. This amplitude is a possible explanation for the significant, experimental discrepancy in the determination of the ratio of the proton electric to magnetic form factors, $R=\mu_p G_E^p/G_M^p$, determined using Rosenbluth separation and polarization transfer techniques. A measurement of the elastic scattering cross section ratio, $\sigma_{e^+p}/\sigma_{e^-p}$, will provide a direct measurement of the two-photon exchange amplitude. The OLYMPUS experiment was carried out at the DESY laboratory in Hamburg, Germany using the 2.01 GeV electron and positron beams of the DORIS storage ring incident on an internal hydrogen gas target. Independent luminosity monitors were operated in parallel to the main spectrometer during data taking to allow for a precise relative luminosity measurement. Approximately 4.45 fb$^{-1}$ of data were collected. The OLYMPUS experiment and the status of the analysis will be discussed.
Speaker: Dr Uwe Schneekloth (DESY)
• 16:50
Double scattering production of two ρ0 mesons and four pions in ultraperipheral heavy ion collisions(remote) 20m
We will discuss a possibility to study the $\rho^0(770)$ mesons production in ultrarelativistic ultraperipheral heavy ion collisions. We evaluate for the first time differential distributions for exclusive production of two $\rho^0(770)$ mesons (four charged pions) in the double scattering (photon-Pomeron) process [1]. The results will be compared with the contribution of two-photon mechanism discussed previously in the literature [2]. The double scattering mechanism populates large dimeson invariant masses and large rapidity distance between mesons. The resulting distributions for four pions will be presented and compared to the STAR data [3]. Predictions for the LHC will be shown. We will discuss a possibility of identifying the double scattering mechanism at the LHC energy. The above analysis includes the smearing of $\rho^0$ mass which was presented recently by the ALICE Collaboration [4]. [1] M. Klusek-Gawenda and A. Szczurek, Phys. Rev. C 89 (2013) 024912, [2] M. Klusek, W. Schafer and A. Szczurek, Phys. Lett. B 674 (2009) 92, [3] B. I. Abelev et al. (STAR Collaboration), Phys. Rev. C 81 (2010) 044901, [4] Adam, Jaroslav et al. (ALICE Collaboration), arXiv:1503.09177 [nucl-ex].
Speaker: Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics PAN Krakow)
• 18:00 21:00
Conference dinner (Bus from BINP to the hotel leaves at 18:15. The restaurant “Pechki-lavochki” is located in 350 m from the hotel.) 3h

Bus from BINP to the hotel leaves at 18:15. The restaurant “Pechki-lavochki” is located in 350 m from the hotel.

• Friday, 19 June
• 08:00 09:25
DVCS and prompt photons
Convener: Dr Marc Knecht (CNRS - CPT Marseille)
• 08:00
The DVCS physics program at COMPASS 20m
A major part of the COMPASS-II program will be dedicated to the investigation of generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs), which aim for the most complete description of the partonic structure of the nucleon. GPDs are experimentally accessible via lepton-induced exclusive reactions, in particular the Deeply Virtual Compton Scattering (DVCS). At COMPASS, this process will be investigated using an high intensity muon beam of 160 GeV and a 2.5 m-long liquid hydrogen target. In order to optimize the selection of exclusive reactions at those energies, the target will be surrounded by a new barrel-shaped time-of-flight system to detect the recoiling particles. COMPASS-II will cover the up to now unexplored $x_{Bj}$ domain ranging from 0.01 to 0.15. The ability to change simultaneously the charge and polarization of the muon beam will allow to access the Compton form factor related to the dominant GPD $H$, and thus to provide new experimental constraints on the theoretical GPD models in the intermediate $x_{Bj}$ regime. Moreover, the $x_{Bj}$-dependence of the nucleon transverse size will be investigated by measuring the sum of the DVCS cross-sections corresponding to positive and negative beam polarities. Projections on the achievable accuracies and preliminary results of pilot measurements will be presented.
Speaker: Dr Andrea Ferrero (CEA-Saclay/IRFU/SPhN)
• 08:20
Probing GPDs in photoproduction processes at hadron colliders. 15m
Ultraperipheral reactions in hadron collisions provide new opportunities to investigate the hadron structure through exclusive photoproduction processes. We review the possibility to access the Generalized Parton Distributions in the Timelike Compton Scattering process and in the exclusive production of heavy vector mesons.
Speaker: Dr Dmitry Ivanov (Sobolev Institute of Mathematics)
• 08:35
Revealing transversity GPDs through the production of a rho meson and a photon 15m
Transversity GPDs have yet to be experimentally unraveled. We propose to probe them by studying the electro- or photo- production of a rho meson and a photon. At dominant twist, separating the longitudinal and transverse polarization of the meson allows one to get access to respectively usual (chiral even) and transversity (chiral odd) GPDs.
Speaker: Mr Renaud Boussarie (LPT Orsay)
• 08:50
Speaker: Dr Simon Eidelman (Budker INP)
• 09:10
Measurements with final-state photons in LHCb 15m
Speaker: Mr Vitaly VOROBYEV (BINP)
• 09:25 09:55
Coffee 30m
• 09:55 11:20
Photon collider prospects, new acceleration techniques and future accelerators
Convener: Prof. Valeriy Serbo (Novosibirsk State University)
• 09:55
Future high energy colliders 30m
During the last three decades linear colliders were considered as best machines for detail study of physics in the energy region 0.1-3 TeV. Observation at LHC of the Higgs boson with rather low mass and still nothing else has triggered new strategies in HEP based on large circular colliders for e+e- and pp collisions. In this talk I give a short review of projects ILC, CLIC, FCC, CEPC-SppC, muon and photon colliders.
Speaker: Prof. Valery Telnov (BINP, Novosibirsk Univ.)
• 10:25
Prospects for Higgs and gauge boson measurements in γγ collisions at FCC-e+e-. 20m
The discovery of the Higgs boson at the LHC, together so far with the absence of any phenomena beyond the Standard Model in collisions at center of mass energies up to 8 TeV, has triggered an interest in future colliders to push the energy and precision frontiers in the search of New Physics. The great potential of high-energy hadron colliders to discover new particles and new phenomena are well-known, but now there is a strong scientific case for an electron-positron ($e^{+}e^{-}$) collider performing high precision studies of the Higgs boson and other known particles. One of the Future Circular Collider (FCC) design study, FCC-$e^{+}e^{-}$, is a high-luminosity, high-precision $e^{+}e^{-}$ collider located in the same tunnel as a possible precursor to the hadron collider FCC-hh, and complementary to it. Delivering $e^{+}e^{-}$ center-of-mass collision energies between 90 and at least 350 GeV, FCC-$e^{+}e^{-}$ will be sensitive to possible new phenomena at energies measured in tens of TeV. In addition to $e^{+}e^{-}$ program, the FCC will provide a unique opportunity to study $\gamma \gamma$ interactions at high energies and luminosities. $\gamma \gamma$ effective luminosities using the equivalent photon approximation (EPA) fluxes are explored for the Higgs, as well as for the exclusive W pair, production.
Speaker: Mrs Patricia Rebello Teles (Brazilian Center for Physics Research)
• 10:45
Developments of optical resonators and optical recirculators for Compton X/γ ray machines 20m
Optical resonators and optical recirculators are key elements of Compton X/$\gamma$-ray machines. Such devices could ultimately be used in the design of polarized positron sources for a future linear electron-positron collider and photon sources for an hypothetical photon-photon collider. With regard to their use in laser physics or in time-frequency metrology, these devices have to obey severe constraints when implemented in the vacuum of an electron accelerator. Our group is developing both types of devices. An original recirculator design is being developed for the ELI-NP $\gamma$ ray source. It is an aberration free device that recirculates 32 times a short and high intensity laser pulse. It also allows synchronizing each of the 32 passes with the electron RF cavities within approximately 100 fs. The second topic is a description of R&D on optical resonators dedicated to laser-electron interactions, in particular the ThomX Compton ring. Two different picosecond laser oscillators have been locked to the highest cavity finesse F=30000 ever reached in pulsed regime. We also designed and built a new kind of non-planar cavity, tetrahedron shape, providing circularly polarized eigenmodes. This cavity was installed in the ATF accelerator of KEK and successfully used to produce a high gamma ray flux. Thanks to an original fibre amplifier, 100 kW of average power were stacked inside the cavity.
Speaker: Dr Aurelien Martens (LAL/IN2P3/CNRS)
• 11:05
Photon spectrum and polarization for high conversion efficiency in Compton backscattering process 15m
The paper [1] reviewed the principles of creation of high-energy $\gamma\gamma$ collider. However, after the discovery of Higgs boson, the authors of paper [2] proposed the concept of the so-called low-energy $\gamma\gamma$ collider (for which the required energy of the electrons does not exceed 80 $MeV$, if the energy of the laser photons is equal to 3.5 $eV$) . In both cases it is necessary to use high power lasers ($10^{18}$ $W/cm^2$) to obtain a desired luminosity. The density of photons in a laser flash is so great that the nonlinear interactions and the possibility of multiple scattering of electrons passing through such “light target” should be taken into account when calculating electron-photon collisions. For such powerful lasers, the conversion coefficient - the ratio of the number of scattered photons to the number of initial electrons [1] - in this case may exceed unity. Since the scattering of laser photons on electrons of the incident beam is a stochastic process, the conversion coefficient is nothing more than the average number of emitted photons $\bar{k}$ [3]. Multiple scattering and substantial change in the energy (and in the cross section) of the electrons along the trajectory in the laser pulse will lead to a deviation of collision statistics from the Poisson law. To simulate multiple scattering of electrons in the light target, we developed Monte-Carlo code which takes into account the nonlinearity of the Compton scattering including spin-flip processes which affect the polarization characteristics of the final particles. The results of calculation of the spectra and polarization characteristics of electrons and photons are presented. Contribution of the electron trajectories with the number of collisions $k \ge 2$ results in substantial enrichment of the resulting spectrum by "soft" photons, which leads to some difference in calculated spectrum from the one obtained by CAIN [4]. [1] V. Telnov, NIMA 355 (1995) 3-18 [2] S.A. Bogasz, J. Ellis, L. Lusito et al., arXiv:1208.2827 [3] A.P. Potylitsyn, A.M. Kolchuzhkin, EPL, 100(2012) 24006 [4] P. Chen, G. Horton-Smith, T. Ohgaki, A. W. Weidemann and K. Yokoya, Nucl. Instrum.Meth. A355, 107 (1995)
Speaker: Prof. Alexander Potylitsyn (National Research Tomsk Polytechnic University, National Research Nuclear University “MEPhI”)
• 12:00 13:30
Lunch 1h 30m
• 14:50 15:00
Closing remarks 10m