No Arabic abstract
The study of QCD processes at the LHC will serve two main goals. First, the predictions of Quantum Chromodynamics will be tested and precision measurements will be performed, allowing additional constraints to be established, and providing measurements of the strong coupling constant. Second, QCD processes represent a major part of the background to other Standard Model processes and signals of new physics at the LHC and therefore need to be understood in depth. An overview of various measurements of QCD-related processes to be performed at the LHC is presented, based on final states containing high-pT leptons, photons and jets. Moreover, possible deviations from QCD predictions indicating presence of new physics are discussed.
The ATLAS collaboration has recently reported a 2.6 sigma excess in the search for a heavy resonance decaying into a pair of weak gauge bosons. Only fully hadronic final states are being looked for in the analysis. If the observed excess really originates from the gauge bosons decays, other decay modes of the gauge bosons would inevitably leave a trace on other exotic searches. In this paper, we propose the use of the Z boson decay into a pair of neutrinos to test the excess. This decay leads to a very large missing energy and can be probed with conventional dark matter searches at the LHC. We discuss the current constraints from the dark matter searches and the prospects. We find that optimizing these searches may give a very robust probe of the resonance, even with the currently available data of the 8 TeV LHC.
We perform a Taylor series expansion of Tsallis distribution by assuming the Tsallis parameter $q$ close to 1. The $q$ value shows the deviation of a system from a thermalised Boltzmann distribution. By taking up to first order in $(q-1)$, we derive an analytical result for Tsallis distribution including radial flow. Further, in the present work, we also study the speed of sound ($c_s$) as a function of temperature using the non-extensive Tsallis statistics for different $q$ values and for different mass cut-offs.
We review the prospects for quarkonium-production studies in proton and nuclear collisions accessible during the upcoming phases of the CERN Large Hadron Collider operation after 2021, including the ultimate high-luminosity phase, with increased luminosities compared to LHC Runs 1 and 2. We address the current experimental and theoretical open issues in the field and the perspectives for future studies in quarkonium-related physics through the exploitation of the huge data samples to be collected in proton-proton, with integrated luminosities reaching up to 3/ab, in proton-nucleus and in nucleus-nucleus collisions, both in the collider and fixed-target modes. Such investigations include, among others, those of: (i) the quarkonia produced in association with other hard particles; (ii) the chi(Q) and eta(Q) down to small transverse momenta; (iii) the constraints brought in by quarkonia on gluon PDFs, nuclear PDFs, TMDs, GPDs and GTMDs, as well as on the low-x parton dynamics; (iv) the gluon Sivers effect in polarised-nucleon collisions; (v) the properties of the quark-gluon plasma produced in ultra-relativistic heavy-ion collisions and of collective partonic effects in general; and (vi) double and triple parton scatterings.
The 19/20-parameter p(henomenological)MSSM with either a neutralino or gravitino LSP offers a flexible framework for the study of a wide variety of R-parity conserving MSSM SUSY phenomena at the 7, 8 and 14 TeV LHC. Here we present the results of a study of SUSY signatures at these facilities obtained via a fast Monte Carlo replication of the ATLAS SUSY analysis suite. In particular, we show the ranges of the sparticle masses that are either disfavored or remain viable after all of the various searches at the 7 and 8 TeV runs are combined. We then extrapolate to 14 TeV with both 300 fb^-1 and 3 ab^-1 of integrated luminosity and determine the sensitivity of a jets + MET search to the pMSSM parameter space. We find that the high-luminosity LHC performs extremely well in probing natural SUSY models.
Weak-scale supersymmetry remains to be one of the best-motivated theories of physics beyond the Standard Model. We evaluate the sensitivities of the High Luminosity (HL) and High Energy (HE) upgrades of the LHC to gluinos and stops, decaying through the simplified topologies $tilde{g} to q bar{q} chi^0$, $tilde{g} to t bar{t} chi^0$ and $tilde{t} to t tilde{chi}^0$. Our HL-LHC analyses improve on existing experimental projections by optimizing the acceptance of kinematic variables. The HE-LHC studies represent the first 27 TeV analyses. We find that the HL-(HE-)LHC with 3 ab$^{-1}$ (15 ab$^{-1}$) of integrated luminosity will be sensitive to the masses of gluinos and stops at 3.2 (5.7) TeV and 1.5 (2.7) TeV, respectively, decaying to massless neutralinos.