A. Alikhanyan National Laboratory

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The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 1034 cm−2 s−1 (1027 cm−2 s−1). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ≤ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

Author(s): Collaboration, The ATLAS; Aad, G; Abat, E; Abdallah, J; Abdelalim, AA; Abdesselam, A; Abdinov, O; Abi, BA; Abolins, M; Abramowicz, H; Acerbi, E; Acharya, BS; Achenbach, R; Ackers, M; Adams, DL; Adamyan, F; Addy, TN; Aderholz, M; Adorisio, C; Adragna, P; Aharrouche, M; Ahlen, SP; Ahles, F; Ahmad, A; Ahmed, H; Aielli, G; Åkesson, PF; Åkesson, TPA; Akimov, AV; Alam, SM; Albert, J; Albrand, S; Aleksa, M; Aleksandrov, IN; Aleppo, M; Alessandria, F; Alexa, C; Alexander, G; Alexopoulos, T; Alimonti, G; Aliyev, M; Allport, PP; Allwood-Spiers, SE; Aloisio, A; Alonso, J; Alves, R; Alviggi, MG; Amako, K; Amaral, P; Amaral, SP; Ambrosini, G; Ambrosio, G; Amelung, C; Ammosov, VV; Amorim, A; Amram, N; Anastopoulos, C; Anderson, B; Anderson, KJ; Anderssen, EC; Andreazza, A; Andrei, V; Andricek, L; Andrieux, M-L; Anduaga, XS; Anghinolfi, F; Antonaki, A; Antonelli, M; Antonelli, S; Apsimon, R; Arabidze, G; Aracena, I; Arai, Y; Arce, ATH; Archambault, JP; Arguin, J-F; Arik, E; Arik, M; Arms, KE; Armstrong, SR; Arnaud, M; Arnault, C; Artamonov, A; Asai, S; Ask, S

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m 3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.

A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is m_{H}=125.09±0.21 (stat)±0.11 (syst) GeV.

Neutrino physics with JUNO, An, Fengpeng, An, Guangpeng, An, Qi, Antonelli, Vito, Baussan, Eric, Beacom, John, Bezrukov, Leonid, Blyth, Simon, Brugnera, Riccardo, Avanzini, Margherita Buizza, Busto, Jose, Cabrera, Anatael, Cai, Hao, Cai, Xiao, Cammi, Antonio, Cao, Guofu, Cao, Jun, Chang, Yun, Chen, Shaomin, Chen, Shenjian, Chen, Yixue, Chiesa, Davide, Clemenza, Massimiliano, Clerbaux, Barbara, Conrad, Janet, D’Angelo, Davide, Kerret, Hervé De, Deng, Zhi, Deng, Ziyan, Ding, Yayun, Djurcic, Zelimir, Dornic, Damien, Dracos, Marcos, Drapier, Olivier, Dusini, Stefano, Dye, Stephen, Enqvist, Timo, Fan, Donghua, Fang, Jian, Favart, Laurent, Ford, Richard, Göger-Neff, Marianne, Gan, Haonan, Garfagnini, Alberto, Giammarchi, Marco, Gonchar, Maxim, Gong, Guanghua, Gong, Hui, Gonin, Michel, Grassi, Marco, Grewing, Christian, Guan, Mengyun, Guarino, Vic, Guo, Gang, Guo, Wanlei, Guo, Xin-Heng, Hagner, Caren, Han, Ran, He, Miao, Heng, Yuekun, Hsiung, Yee, Hu, Jun, Hu, Shouyang, Hu, Tao, Huang, Hanxiong, Huang, Xingtao, Huo, Lei, Ioannisian, Ara, Jeitler, Manfred, Ji, Xiangdong, Jiang, Xiaoshan, Jollet, Cécile, Kang, Li, Karagounis, Michael, Kazarian, Narine, Krumshteyn, Zinovy, Kruth, Andre, Kuusiniemi, Pasi, Lachenmaier, Tobias, Leitner, Rupert, Li, Chao, Li, Jiaxing, Li, Weidong, Li, Weiguo, Li, Xiaomei, Li, Xiaonan, Li, Yi, Li, Yufeng, Li, Zhi-Bing, Liang, Hao, Lin, Guey-Lin, Lin, Tao, Lin, Yen-Hsun, Ling, Jiajie, Lippi, Ivano, Liu, Dawei, Liu, Hongbang, Liu, Hu, Liu, Jianglai, Liu, Jianli, Liu, Jinchang, Liu, Qian, Liu, Shubin, Liu, Shulin, Lombardi, Paolo, Long, Yongbing, Lu, Haoqi, Lu, Jiashu, Lu, Jingbin, Lu, Junguang, Lubsandorzhiev, Bayarto, Ludhova, Livia, Luo, Shu, Vladimir Lyashuk, Möllenberg, Randolph, Ma, Xubo, Mantovani, Fabio, Mao, Yajun, Mari, Stefano M, McDonough, William F, Meng, Guang, Meregaglia, Anselmo, Meroni, Emanuela, Mezzetto, Mauro, Miramonti, Lino, Thomas Mueller, Naumov, Dmitry, Oberauer, Lothar, Ochoa-Ricoux, Juan Pedro, Olshevskiy, Alexander, Ortica, Fausto, Paoloni, Alessandro, Peng, Haiping, Jen-Chieh Peng, Previtali, Ezio, Qi, Ming, Qian, Sen, Qian, Xin, Qian, Yongzhong, Qin, Zhonghua, Raffelt, Georg, Ranucci, Gioacchino, Ricci, Barbara, Robens, Markus, Romani, Aldo, Ruan, Xiangdong, Ruan, Xichao, Salamanna, Giuseppe, Shaevitz, Mike, Valery Sinev, Sirignano, Chiara, Sisti, Monica, Smirnov, Oleg, Soiron, Michael, Stahl, Achim, Stanco, Luca, Steinmann, Jochen, Sun, Xilei, Sun, Yongjie, Taichenachev, Dmitriy, Tang, Jian, Tkachev, Igor, Trzaska, Wladyslaw, Waasen, Stefan van, Volpe, Cristina, Vorobel, Vit, Votano, Lucia, Wang, Chung-Hsiang, Wang, Guoli, Wang, Hao, Wang, Meng, Wang, Ruiguang, Wang, Siguang, Wang, Wei, Wang, Yi, Wang, Yi, Wang, Yifang, Wang, Zhe, Wang, Zheng, Wang, Zhigang, Wang, Zhimin, Wei, Wei, Wen, Liangjian, Wiebusch, Christopher, Wonsak, Björn, Wu, Qun, Wulz, Claudia-Elisabeth, Wurm, Michael, Xi, Yufei, Xia, Dongmei, Xie, Yuguang, Zhi-zhong Xing, Xu, Jilei, Yan, Baojun, Yang, Changgen, Yang, Chaowen, Yang, Guang, Yang, Lei, Yang, Yifan, Yao, Yu, Yegin, Ugur, Yermia, Frédéric, You, Zhengyun, Yu, Boxiang, Yu, Chunxu, Yu, Zeyuan, Zavatarelli, Sandra, Zhan, Liang, Zhang, Chao, Zhang, Hong-Hao, Zhang, Jiawen, Zhang, Jingbo, Zhang, Qingmin, Zhang, Yu-Mei, Zhang, Zhenyu, Zhao, Zhenghua, Zheng, Yangheng, Zhong, Weili, Zhou, Guorong, Zhou, Jing, Zhou, Li, Zhou, Rong, Zhou, Shun, Zhou, Wenxiong, Zhou, Xiang, Zhou, Yeling, Zhou, Yufeng, Zou, Jiaheng

Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a W or a Z boson or a pair of top quarks, and of the six decay modes H → ZZ, W W , γγ, ττ, bb, and μμ. All results are reported assuming a value of 125.09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton-proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb$^{−1}$ at $\sqrt{s}$=7 TeV and 20 fb−1 at $\sqrt{s}$=8 TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1.09 ± 0.11. The combined measurements lead to observed significances for the vector boson fusion production process and for the H → ττ decay of 5.4 and 5.5 standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered.

During 2015 the ATLAS experiment recorded [Formula: see text] of proton-proton collision data at a centre-of-mass energy of [Formula: see text]. The ATLAS trigger system is a crucial component of the experiment, responsible for selecting events of interest at a recording rate of approximately 1 kHz from up to 40 MHz of collisions. This paper presents a short overview of the changes to the trigger and data acquisition systems during the first long shutdown of the LHC and shows the performance of the trigger system and its components based on the 2015 proton-proton collision data.

The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer.A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider.For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic τ decay reconstruction, missing transverse momentum determination, and electron and muon identification.This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods.The data collected by CMS at a centre-of-mass energy of 8 TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions.

Abada, A. et al.

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5–10 improvement in sensitivity in the 100 GeV–10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (φ).Short-range correlations in ∆η, which are studied in minimum bias events, are characterized using a simple "independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width).Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb -1 data set at 7 TeV.In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate p T of 1-3 GeV/c, 2.0 < |∆η| < 4.8 and ∆φ ≈0.This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or pp collisions.

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at $\sqrt{{s}_{NN}}=2.76\text{ }\text{ }\mathrm{TeV}$ with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region ($|\ensuremath{\eta}|<0.8$) and transverse momentum range $0.2<{p}_{t}<5.0\text{ }\text{ }\mathrm{GeV}/c$. The elliptic flow signal ${v}_{2}$, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is $0.087\ifmmode\pm\else\textpm\fi{}0.002(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.003(\mathrm{syst})$ in the 40%--50% centrality class. The differential elliptic flow ${v}_{2}({p}_{t})$ reaches a maximum of 0.2 near ${p}_{t}=3\text{ }\text{ }\mathrm{GeV}/c$. Compared to RHIC Au-Au collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

Context.The Crab nebula was observed with the HESS stereoscopic Cherenkov-telescope array between October 2003 and January 2005 for a total of 22.9 h (after data quality selection). This period of time partly overlapped with the commissioning phase of the experiment; observations were made with three operational telescopes in late 2003 and with the complete 4 telescope array in January–February 2004 and October 2004–January 2005.

The high-frequency peaked BL Lac PKS 2155-304 at redshift z = 0.116 is a well-known VHE (>100 GeV) γ-ray emitter. Since 2002 its VHE flux has been monitored using the H.E.S.S. stereoscopic array of imaging atmospheric Cerenkov telescopes in Namibia. During the 2006 July dark period, the average VHE flux was measured to be more than 10 times typical values observed from the object. This article focuses solely on an extreme γ-ray outburst detected in the early hours of 2006 July 28 (MJD 53,944). The average flux observed during this outburst is I (>200 GeV) = (1.72 ± 0.05 stat ± 0.34 syst ) × 10 -9 cm -2 s -1 , corresponding to ~7 times the flux, I (>200 GeV), observed from the Crab Nebula. Peak fluxes are measured with 1 minute timescale resolution at more than twice this average value. Variability is seen up to ~600 s in the Fourier power spectrum, and well-resolved bursts varying on timescales of ~200 s are observed. There are no strong indications for spectral variability within the data. Assuming the emission region has a size comparable to the Schwarzschild radius of a ~10 9 M ☉ black hole, Doppler factors greater than 100 are required to accommodate the observed variability timescales.

This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, $\tau$ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described.

A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of p T > 0.9GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p T = 100GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in p T , and respectively, 10μm and 30μm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10–12μm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung.

By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.

Properties of the Higgs boson with mass near 125[Formula: see text] are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1[Formula: see text] at 7[Formula: see text] and up to 19.7[Formula: see text] at 8[Formula: see text]. From the high-resolution [Formula: see text] and [Formula: see text] channels, the mass of the Higgs boson is determined to be [Formula: see text]. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is [Formula: see text] at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.

collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to [Formula: see text] over most of the covered phase space ([Formula: see text] and [Formula: see text] GeV). The isolation efficiency varies between 93 and [Formula: see text] depending on the selection applied and on the momentum of the muon. Both efficiencies are well reproduced in simulation. In the central region of the detector, the momentum resolution is measured to be [Formula: see text] ([Formula: see text]) for muons from [Formula: see text] ([Formula: see text]) decays, and the momentum scale is known with an uncertainty of [Formula: see text]. In the region [Formula: see text], the [Formula: see text] resolution for muons from [Formula: see text] decays is [Formula: see text] while the precision of the momentum scale for low-[Formula: see text] muons from [Formula: see text] decays is about [Formula: see text].