### CERN Proceedings, Vol 1 (2019): Proceedings of the 15th International Conference on Nuclear Reaction Mechanisms

CERN Proceedings
Varenna (Italy), Villa Monastero, June 11–15, 2018 Editors: F. Cerutti, A. Ferrari, T. Kawano, F. Salvat-Pujol, and P. Talou ISBN 978-92-9083-519-6 (paperback) ISBN 978-92-9083-520-2 (PDF)

### CERN Proceedings, Vol 1 (2017): CERN-BINP Workshop for Young Scientists in e+e- Colliders

CERN Proceedings
Geneva, Switzerland, 22--25 August 2016 Edited by V. Brancolini and L. Linssen CERN-Proceedings-2017-001, ISBN 978-92-9083-451-9 (print), ISBN 978-92-9083-452-6 (PDF) This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement no. 654166.

### CERN Proceedings, Vol 1 (2018): Proceedings of the PHOTON'17 Conference

CERN Proceedings
Geneva, Switzerland, 22 - 26 May 2017 Edited by David d'Enterria, Albert de Roeck and Michelangelo Mangano CERN-Proceedings-2018-001, ISBN 978–92–9083–512–7 (print), ISBN 978–92–9083–513–4 (PDF)

### CERN Proceedings, Vol 2 (2017): Proceedings of the Injector MD Days 2017

CERN Proceedings
Geneva, Switzerland, 23--24 March 2017 Edited by H. Bartosik and G. Rumolo CERN-Proceedings-2017-002, ISBN 978-92-9083-474-8 (print), ISBN 978-92-9083-475-5 (PDF)

### Estimating gluon saturation in dijet photoproduction in UPC

Piotr Kotko
We study dijet production in the ultra-peripheral heavy ion collisions (UPC) at LHC within the saturation formalism. More precisely, we use an approach which is the large-$p_T$ approximation to the Color Glass Condensate on one hand, and the small-$x$ limit of the transverse momentum dependent (TMD) factorization on the other. The direct component of the dijet production in UPC at small $x$ probes the so-called Weizsacker-Williams (WW) TMD gluon distribution, which is not accessible in...

### Anomalous gauge interactions in photon collisions at the LHC and the FCC

Sylvain Fichet & Cristian Baldenegro
The forward proton detectors recently installed and operating at the LHC open the possibility to observe photon collisions with high precision, providing a novel window on physics beyond the Standard Model. We review recent simulations and theoretical developments about the measurement of anomalous $\gamma\gamma\gamma\gamma$ and $Z\gamma\gamma\gamma$ interactions. The searches for these anomalous gauge interactions are expected to set bounds on a wide range of particles including generic electroweak particles, neutral particles with dimension-5 coupling to...

### The photon PDF from high-mass Drell-Yan data at the LHC

Valerio Bertone
I present a determination of the photon PDF from a fit to the recent ATLAS measurements of high-mass Drell-Yan lepton-pair production at $\sqrt{s} = 8$ TeV. This analysis is based on the {\tt xFitter} framework interfaced to the {\tt APFEL} program, that accounts for NLO QED effects, and to the {\tt aMCfast} code to account for the photon-initiated contributions within {\tt MadGraph5\_aMC@NLO}. The result is compared with other recent determinations of the photon PDF finding...

### Preface PHOTON'17 conference proceedings

David Enterria
The PHOTON 2017 conference (International Conference on the Structure and the Interactions of the Photon'', including the 22th International Workshop on Photon-Photon Collisions, and the International Workshop on High Energy Photon Colliders'') was held at CERN (Geneva) from 22th to 26th May, 2017. The conference is part of a series that was initiated in 1973 in Paris as International Colloquium on Photon-Photon Collisions at Electron-Positron Storage Rings''. The latest Photon conferences took place in Novosibirsk...

### Prospects for $\gamma\gamma\to$ Higgs observation in ultraperipheral ion collisions at the Future Circular Collider

David Enterria, Daniel E. Martins & Patricia Rebello Teles
We study the two-photon production of the Higgs boson, $\gamma\gamma\to H$, at the Future Circular Collider (FCC) in ultraperipheral PbPb and pPb collisions at $\sqrt{s_{NN}} = 39$ and 63 TeV. Signal and background events are generated with MadGraph-5, including $\gamma$ fluxes from the proton and lead ions in the equivalent photon approximation, yielding $\sigma(\gamma\gamma\to H)$ = 1.75 nb and 1.5 pb in PbPb and pPb collisions respectively. We analyse the H$\to b\bar{b}$ decay mode including...

### Photon-photon measurements in CMS

Ruchi Chudasama
We discuss the measurement of photon-photon processes using data collected by the CMS experiment in pp collisions at sqrt(s) = 7 and sqrt(8) TeV and in PbPb collisions at sqrt(s_NN) =5.02 TeV.

### Maria Krawczyk : friend and physicist

Rohini M. Godbole & Giulia Pancheri
We remember here our friend and colleague Maria Krawczyk, Professor of Physics at Warsaw University, who passed away suddenly on May 24th 2017. Her contribution to physics and her great personal qualities are described.

### Quarkonium-photoproduction prospects at a fixed-target experiment at the LHC (AFTER@LHC)

Laure Marie Massacrier, Jean-Philippe Lansberg, Lech Szymanowski & Jakub Wagner
We report on the potentialities offered by a fixed-target experiment at the LHC using the proton and ion LHC beams (AFTER@LHC project) regarding the study of J/psi exclusive-photoproduction in pA and AA collisions. The foreseen usage of polarised targets (hydrogen, deuteron, helium) gives access to measurements of the Single-Transverse-Spin Asymmetries of this exclusive process, therefore allowing one to access the helicity-flip Generalised Parton Distribution (GPD) Eg. We detail the expected yields of photoproduced J/psi in...

### Photon-proton and photon-nucleus measurements in CMS

Ruchi Pravin Chudasama
The CMS measurements of exclusive photoproduction of Υ in pPb and J/ψ in PbPb collisions, that probe the low-x gluon density in the proton and the lead nucleus respectively, are discussed.

### Constraint on Born-Infeld Theory from Light-by-Light Scattering at the LHC

Jonathan Richard Ellis, Nikolaos Mavromatos & Tevong You
The recent measurement by ATLAS of light-by-light scattering in LHC Pb- Pb collisions is the first direct evidence for this basic process. We find that it excludes a range of the mass scale of a nonlinear Born-Infeld extension of QED that is

### Gamma-gamma Collider – A Brief History and Recent Developments

Weiren Chou
There is renewed interest in constructing a gg collider following the discovery of the Higgs boson and the formation of an ICFA (International Committee for Future Accelerators) – ICUIL (International Committee on Ultrahigh Intensity Lasers) collaboration. ICUIL brings state-of-the-art laser technology to build new types of accelerators such as a gg collider. A recent ICFA mini-workshop on gg colliders investigated the possibility and physics value of a low energy gg collider. This paper uses a...

### Latest results on Higgs $\to\gamma\gamma$ in the CMS experiment

Hamed Bakhshiansohi
Photonic decay of the Higgs boson is one of the most prominent decay modes for the observation and measurement of the Higgs boson properties, although its rate is as low as 0.002. The CMS collaboration has analyzed 35.9fb$^{-1}$ of proton-proton collision data delivered by LHC at the center of mass energy of 13~TeV. The inclusive results of the search in different Higgs production mechanisms and the differential fiducial cross section measurement results are presented in...

### The LHC Ring as a Photon-Photon Search Machine

Risto Orava
The LHC Collider Ring can be turned into a photon-photon search machine based on Central Exclusive Process (CEP): pp -> p + X + p. The present extensive Beam Loss Monitoring (BLM) system of the LHC precisely registers the exit points of the final state CEP protons according to their longitudinal momentum losses. The BLM system is being continuously extended, and equipped with fast timing and data acquisition systems, will enable efficient new physics event...

### Exploring pseudo-Nambu-Goldstone bosons in the sub-eV to 10 keV mass range with stimulated photon collider

Kensuke Homma
Generic laboratory searches for pseudo-Nambu-Goldstone bosons (pNGBs) in weak-coupling domains beyond the GUT scale are indispensable for understanding the dark components in the universe. We introduce a novel approach to search for resonantly produced pNGBs coupled to two photons in the mass range from sub-eV to 10~keV by colliding plural laser fields to induce the rare scattering process.

### Very forward photon production in proton-proton collisions at √s = 13 TeV measured with the LHCf experiment

Alessio Tiberio
The latest physics results of LHCf photon analysis are reported in this paper. The inclusive energy spectrum of photons produced in proton-proton collisions at √s = 13 TeV are shown. The results are compared with the prediction of hadronic interaction models commonly used in air-shower simulations of ultra-high-energy cosmic rays. Even if experimental data lie between the models, there is not a single model consistent with data in all the energy range. The better overall...

### Status of the light-by-light scattering and the $(g-2)_{\mu}$

Pere Masjuan Queralt
In this talk we review the recent progress on the numerical determination of the Hadronic Light-by-Light contribution to the anomalous magnetic moment of the muon and we discuss the role of experimental data on the accuracy of its determination. Special emphasis on the main contribution, the pseudoscalar piece, is made. Gathering recent progress in the light-by-light scattering contribution we consider $a_{\mu}^{{\mathrm{HLBL}}} = (12.1\pm3.0)\times10^{-10}$ as a good summary of the state-of-the-art calculations which still claims for...

### Search for Extensive Photon Cascades with the Cosmic-Ray Extremely Distributed Observatory

Piotr Homola
Although the photon structure is most efficiently studied with the accelerator instruments, there is also a scientifically complementary potential in investigations on photons produced in the outer space. This potential is already being explored with gamma ray telescopes, ultra-high energy cosmic ray observatories and, since very recently, by the Cosmic-Ray Extremely Distributed Observatory (CREDO). Unlike the former instruments focused on detection of single photons, CREDO aims at the detection of cascades (ensembles) of photons originating...

### Photoproduction with a mini-jet model and Cosmic Ray showers

Fernando Cornet, Carlos Garcia-Canal, Agnes Grau, Giulia Pancheri & Sergio Sciutto
We present post-LHC updates of estimates of the total photo-production cross section in a mini-jet model with infrared soft gluon resummation, and apply the model to study Cosmic Ray shower development, comparing the results with those obtained from other existing models.

### Search for Ultra-High Energy Photons with the Pierre Auger Observatory

Piotr Homola
One of key scientific objectives of the Pierre Auger Observatory is the search for ultra-high energy photons. Such photons could originate either in the interactions of energetic cosmic-ray nuclei with the cosmic microwave background (so-called cosmogenic photons) or in the exotic scenarios, e.g. those assuming a production and decay of some hypothetical super-massive particles. The latter category of models would imply relatively large fluxes of photons with ultra-high energies at Earth, while the former, involving...

### Photoproduction of vector mesons in ultra-peripheral Pb-Pb interactions with ALICE

Christopher Daniel Anson
Cross section measurements for vector meson production in ultra-peripheral collisions provide important insight into nuclear gluon distributions, the production mechanisms of vector mesons and a better understanding of the early stages of heavy ion collisions. With data collected during LHC \mbox{Run 1}, \mbox{ALICE} measured vector meson production in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. Detector upgrades and improved triggers before LHC \mbox{Run 2} will be discussed. These improvements have allowed a much higher statistics data...

### Two-Photon Measurements in ATLAS

Chav Chhiv Chau
At the Large Hadron Collider, two-photon production is a key process for studying photon interactions at high energies. Measurements of two-photon processes provide a direct access to the photon distribution function in protons and nuclei, and can probe the couplings between four vector bosons ($WW\gamma\gamma$) to find any deviation from the Standard Model. Two-photon measurements reported by the ATLAS Collaboration are presented. These measurments are performed using the proton-proton collisions at the centre-of-mass energy of...

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