This report provides an overview of the new results obtained by the ATLAS Collaboration at the LHC, which were presented at the Quark Matter 2018 conference. Furthermore these measurements were ...covered in 12 parallel talks, one flash talk and 11 posters. In this document, a discussion of results is grouped into four areas: electromagnetic interactions, jet quenching, quarkonia and heavy-flavour production, and collectivity in small and larger systems. Measurements from the xenon-xenon collisions based on a short run collected in October 2017 are reported for the first time.
Photons and weak bosons do not interact strongly and, thus, their production yields provide direct tests of scaling with a number of binary nucleon–nucleon collisions in the heavy-ion environment. In ...addition, they should be sensitive to the nuclear modification of parton distribution functions (nPDF). Proton-lead collisions also provide an excellent opportunity to test nPDF in a less dense environment than lead–lead via looking at forward–backward production of weak bosons. The ATLAS detector has proven to be an excellent apparatus in measurements involving photons, electrons and muons, the latter being products of weak boson decays, in the high occupancy environment produced in heavy-ion collisions. The experiment has recorded 30nb−1 of proton–lead data and 140μb−1 of lead–lead data, both of which have similar integrated partonic luminosities. We present the prompt photon, Z and W boson yields as a function of centrality, and also differentially in transverse momentum and rapidity, in lead–lead and proton–lead collisions from the ATLAS experiment. For W± bosons, a lepton charge asymmetry has also been studied, which may also shed light on nPDF.
Electroweak–boson production processes (W, Z and photon) provide access to the earliest moments of heavy–ion collisions. Furthermore, because they do not undergo strong interactions, they are ...sensitive to the initial–state geometry of the collision and potentially the details of the nuclear parton distribution functions. ATLAS results on vector–boson yields have demonstrated binary collision scaling in Pb+Pb collisions. In p + Pb collisions, the measurement of vector bosons provides possible constraints on the nuclear parton distribution functions and insights into the details of the initial collision geometry. We report on the latest results of vector–boson production in p + Pb collisions at sNN=5.02 TeV. Production yields of Z and W bosons and lepton charge asymmetry of W bosons are presented as a function of pseudo-rapidity and centrality. The vector–boson yields are compared to calculations incorporating different parton distribution functions, as well as different centrality calculations.
Opportunities for searches for phenomena beyond the Standard Model (BSM) using heavy-ions beams at high energies are outlined. Different BSM searches proposed in the last years in collisions of heavy ...ions, mostly at the Large Hadron Collider, are summarized. A few concrete selected cases are reviewed including searches for axion-like particles, anomalous \(\tau\) electromagnetic moments, magnetic monopoles, and dark photons. Expectations for the achievable sensitivities of these searches in the coming years are given. Studies of CP violation in hot and dense QCD matter and connections to ultrahigh-energy cosmic rays physics are also mentioned.
Ultra-peripheral collisions (UPCs) involving heavy ions and protons are the energy frontier for photon-mediated interactions. UPC photons can be used for many purposes, including probing low-\(x\) ...gluons via photoproduction of dijets and vector mesons, probes of beyond-standard-model processes, such as those enabled by light-by-light scattering, and studies of two-photon production of the Higgs.
Two results in ep physics using HERA data are discussed: a measurement of the
effective transverse parton momentum in the proton by studying the production
of prompt-photons in photoproduction events ...in the ZEUS collaboration and
differential cross sections for Deeply Virtual Compton Scattering obtained by
both the H1 and ZEUS collaborations.
Two results in ep physics using HERA data are discussed: a measurement of the effective transverse parton momentum in the proton by studying the production of prompt-photons in photoproduction events ...in the ZEUS collaboration and differential cross sections for Deeply Virtual Compton Scattering obtained by both the H1 and ZEUS collaborations.
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