ATLAS reach for Quarkonium cross section and polarization measurement
Erez Etzion, Jony Ginzburg
备注：
8 pages, 7 figures, presented at 8th International Conference on Hyperons, Charm and Beauty Hadrons, Columbia, SC, USA, 22 - 28 Jun 2008, submitted to Nuclear Physics B -- Proceeding Supplements (NUPHBP) by Elsevier
The ATLAS detector at CERN's LHC is preparing to take data from the first proton-proton collisions expected in the next few months. We report on the analysis of simulated data samples for production of heavy Quarkonium states J/psi and Upsilon, corresponding to an integrated luminosity of 10 pb^-1 with center of mass energy of 14 TeV expected at the early ATLAS data. We review various aspects of prompt Quarkonium production at LHC: the accessible ranges in transverse momentum and pseudorapidity, spin alignment of vector states, separation of color octet and color singlet production mechanism and feasibility of observing radiative decays Xi_c and Xi_b decays. Strategies of various measurements are outlined and methods of separating promptly produced J/psi and Upsilon mesons from various backgrounds are discussed.
The modification of the production of $J/ψ$, $ψ(\mathrm{2S})$, and $\mitΥ(n\mathrm{S})$ ($n = 1, 2, 3$) in $p$+Pb collisions with respect to their production in $pp$ collisions has been studied. The $p$+Pb and $pp$ datasets used in this paper correspond to integrated luminosities of $28$ $\mathrm{nb}^{-1}$ and $25$ $\mathrm{pb}^{-1}$ respectively, collected in 2013 and 2015 by the ATLAS detector at the LHC, both at a centre-of-mass energy per nucleon pair of 5.02 TeV. The quarkonium states are reconstructed in the dimuon decay channel. The yields of $J/ψ$ and $ψ(\mathrm{2S})$ are separated int…
Searches for exclusive Higgs and $Z$ boson decays into a vector quarkonium state and a photon using $139$ fb$^{-1}$ of ATLAS $\sqrt{s}=13$ TeV proton$-$proton collision data
In view of the large discrepancy about the associated production of a prompt $J/ψ$ and a $Z$ boson between the ATLAS data at $\sqrt{s}=8$ TeV and theoretical predictions for Single Parton Scattering (SPS) contributions, we perform an evaluation of the corresponding cross section at one loop accuracy (Next-to-Leading Order, NLO) in a quark-hadron-duality approach, also known as the Colour-Evaporation Model (CEM). This work is motivated by (i) the extremely disparate predictions based on the existing NRQCD fits conjugated with the absence of a full NLO NRQCD computation and (ii) the fact that we…
The potential of the ALICE, ATLAS, CMS and LHCb detectors for the measurement of quarkonium in heavy-ion collisions, both in nucleus-nucleus (A-A) and in proton-nucleus (p-A) interactions, in the years 2015 until about 2030 in the LHC Runs 2, 3 and 4 with larger statistics and detector upgrades is described. A selection of newly available observables is discussed.
Two recent analyses of data collected with the ATLAS detector at the Large Hadron Collider are presented. In the first, a measurement of $b$ hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb$^{-1}$ of proton-proton collisions recorded at $\sqrt{s}=8$ TeV. Events are selected in which a $b$ hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume defined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be $17.7 \pm 0.1…
The production process of quarkonia in proton-proton (pp) collision is a very good probe of the parton structure of the proton. Recent experimental data of the production of J/psi+vector boson or quarkonium pairs at the LHC and Tevatron suggest the relevance of double parton scatterings (DPS). We discuss here the single parton scattering (SPS) contribution to the J/psi +Z, J/psi +W, and J/psi +J/psi productions in hadron collisions. By revisiting the computations of the SPS contributions to the J/psi+Z and J/psi +W productions, we demonstrate that the ATLAS data in fact show evidence for DPS.
The measurements of b quark, quarkonium and exotic state production performed with the ATLAS and CMS experiments at sqrt(s)=7 TeV are presented. The b-quark production cross section is measured both in inclusive and fully reconstructed B hadron decays. The results are compared with QCD expectations at tree-level and NLO.
The ATLAS and CMS Plans for the LHC Luminosity Upgrade
2007年1月，CERN总干事宣布了LHC光度升级的计划。该计划预计第1阶段升级达到峰值亮度$3 \times 10^{34}$ cm $^{-2}$ s $^{-1}$，随后阶段达到$ 10^{35}$ cm $^{-2}$ s $^{-1}$。我们讨论的物理潜力和实验挑战的升级LHC运行。文中还讨论了在高辐射环境中运行ATLAS和CMS所需的探测器研发和预期的探测器性能。
Quarkonia, i.e. bound states of $b\bar{b}$ and $c\bar{c}$ quarks, are powerful observables to study the properties of nuclear matter under extreme conditions. The formation of a Quark-Gluon Plasma (QGP), which is predicted by lattice QCD calculations at high temperatures as reached at LHC energies, has a strong influence on the production and behavior of quarkonia. The latest ALICE results on bottomonium and charmonium production in nucleus$-$nucleus collisions are presented. This includes measurements of the $Υ$(1S) and $Υ$(2S) nuclear modification factors ($R_{\mathrm{AA}}$) at forward rapid…
The ATLAS detector at the LHC is equipped with dedicated systems designed for the detection of forward protons produced in diffractive and photon-induced processes. These detectors significantly extend the ATLAS physics reach. Recent measurements performed using these forward proton detectors: elastic proton-proton scattering, exclusive charged pion-pair production, and two-photon production of lepton pairs are presented.
We study the Single-Parton-Scattering (SPS) production of double quarkonia (J/psi+J/psi, J/psi+Upsilon, and Upsilon+Upsilon) in pp and pp(bar) collisions at the LHC and the Tevatron as measured by the CMS, ATLAS, LHCb, and D0 experiments in the Colour-Evaporation Model (CEM), based on the quark-hadron-duality, including Next-to-Leading Order (NLO) QCD corrections up to alpha_s^5. To do so, we also perform the first true NLO --up to alpha_s^4-- study of the p_T-differential cross section for single-quarkonium production. This allows us to fix the non-perturbative CEM parameters at NLO accuracy …
We show that the production of J/psi or Upsilon pairs in unpolarised pp collisions is currently the best process to measure the momentum-distribution of linearly-polarised gluons inside unpolarised protons through the study of azimuthal asymmetries. Not only the short-distance coefficients for such reactions induce the largest possible cos 4 phi modulations, but analysed data are already available. Among the various final states previously studied in unpolarised pp collisions within the TMD factorisation approach, di-J/psi production exhibits by far the largest asymmetries, up to 50% in the re…
Observation and measurements of the production of prompt and non-prompt $J/ψ$ mesons in association with a $Z$ boson in $pp$ collisions at $\sqrt{s}= 8$ TeV with the ATLAS detector
Although the existence of dark matter is well established by many astronomical measurements, its nature still remains one of the unsolved puzzles of particles physics. The unprecedented energy reached by the Large Hadron Collider (LHC) at CERN has allowed exploration of previously unaccessible kinematic regimes in the search for new phenomena. An overview of most recent searches for dark matter with the ATLAS detector at LHC is presented and the interpretation of the results in terms of effective field theory and simplified models is discussed. The exclusion limits set by the ATLAS searches ar…
Events containing a pair of high energy hadronic jet can provide clear signatures in the search for new physics at high energy hadron colliders. The ATLAS and CMS experiments collected the data from LHC collisions at $\sqrt{s}$= 13 TeV during 2015 and 2016, looking for evidence of new resonances or deviations from the Standard Model predictions. Althoug no hint of new physics was seen, strong limits have been set on the most interesting benchmark models, improving LHC Run1 reach.
Quarkonium is the bound state of a heavy quark and its anti-quark counterpart. The study of this system has experienced a renaissance thanks to results from e+e- collider experiments, including discoveries of long-predicted conventional quarkonia, and unusual states consisting of four quarks. The Belle Experiment operated at KEK in Japan from 1999-2010. Analysis of the collected data continues to produce new findings. The Belle II experiment is a substantial upgrade of both the Belle detector and the KEKB accelerator, aiming to collect 50 times more data beginning in 2018. This talk presented …
Several electroweak precision measurements are performed by the ATLAS and CMS collaborations at the LHC. The main ones are carried out using Drell-Yan production of single W and Z boson. They regard the measurement of the production cross sections of W and Z bosons, the mass of the W boson, and $\sin^2θ_W$. The results of the $\sin^2θ_W$ measurements have an accuracy of approximately twice that reached at LEP and SLD. Other measurements reported are about the Drell-Yan differential production cross section.
High-precision measurements of the Drell-Yan production provide information on different aspects contributing to the process, such as parton distribution functions (PDFs), and comparisons with the current precision reached theoretically on the calculations of the cross sections of such processes. This document describes ATLAS measurements, performed at different centre-of-mass energies, of vector boson (W and Z) cross sections and cross-section ratios. It also discusses measurements of ratios of Z-boson and top-quark pair production cross sections, which provide important information on the pr…
In a previous paper, we had modified Non-Relativistic QCD as it applies to quarkonium production by taking into account the effect of perturbative soft-gluon emission from the colour-octet quarkonium states. We tested the model by fitting the unknown non-perturbative parameter in the model from Tevatron data and using that to make parameter-free predictions for $J/ψ$ and $ψ'$ production at the LHC. In this paper, we study $χ_c$ production: we fit as before the unknown matrix-element using data from Tevatron. We, then, extend the results of the previous paper for $J/ψ$ production by calculating…
High-precision measurements of Standard Model processes provide information on different aspects contributing to the process, such as parton distribution functions, and comparisons with the current precision reached theoretically on the calculations of the cross sections of such processes. This document describes ATLAS measurements, performed at different centre-of-mass energies, of vector boson (W and Z) cross sections and cross-section ratios. It also discusses measurements of ratios of Z-boson and top-quark pair production cross sections, which provide important information on the proton PD…
LHC团队所采取的路径达到3.6 10 $^{33}$ cm $^{-2}$ s $^{-1}$瞬时光度，并提供5.6 fb $^{-1}$每个实验的总结。这两个实验的主要表现突出，特别是他们设法应付已经很高的水平的“堆积”的方式。给出了部分标准模型和最高物理结果，并总结了每个实验对希格斯玻色子玻色子搜索的限制状况。最后对超对称性和奇异现象的研究作了简要的概述。
With the large data set delivered during the second run of the CERN LHC, inclusive and differential measurements of the top quark-antiquark production cross section at the ATLAS and CMS experiments often reach a precision that is comparable or superior to that of the corresponding theoretical calculations. The results of these measurements can be used to test the validity of perturbative quantum chromodynamics (QCD), and to precisely extract the values of parameters of the QCD Lagrangian such as the top quark mass ($m_\mathrm{t}$). The value of $m_\mathrm{t}$ can also be measured, with higher …
Results of dedicated Monte Carlo simulations of beam-induced background (BIB) in the ATLAS experiment at the Large Hadron Collider (LHC) are presented and compared with data recorded in 2012. During normal physics operation this background arises mainly from scattering of the 4 TeV protons on residual gas in the beam pipe. Methods of reconstructing the BIB signals in the ATLAS detector, developed and implemented in the simulation chain based on the FLUKA Monte Carlo simulation package, are described. The interaction rates are determined from the residual gas pressure distribution in the LHC ri…
A search for R-parity violating supersymmetry in final states characterised by high jet multiplicity, at least one isolated light lepton and either zero or at least three $b$-tagged jets is presented. The search uses 139 fb$^{-1}$ of $\sqrt{s} = 13$ TeV proton-proton collision data collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature gluino production, top-squark production, or electroweakino production. The dominant sources of background are estimated using a data-driven …
A search for resonances in the dielectron and dimuon mass spectra from 250 GeV to 6 TeV is presented. The data were recorded during Run 2 of the LHC by the ATLAS experiment using proton-proton ($pp$) collisions with a center-of-mass energy of $\sqrt{s} = 13$ TeV. The integrated luminosity of the data corresponds to 139 fb$^{-1}$. The background models are a functional form fit to the data, and generic signal shapes are used to represent various models with different resonant widths and masses. No significant deviation from the expected background is observed and 95\% confidence level upper lim…
The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton--proton collision data at a center-of-mass energy of $\sqrt{s}$ = 13 TeV are presented. The dataset used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 $fb^{-1}$. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 Te…
