The dimuon invariant mass spectrum is searched in the range between 5.5 and 14 GeV for a light pseudoscalar Higgs boson "a", predicted in a number of new physics models, including the next-to-minimal supersymmetric standard model. The data sample used in the search corresponds to an integrated luminosity of 1.3 inverse femtobarns collected in pp collisions at sqrt(s) = 7 TeV with the CMS detector at the LHC. No excess is observed above the background predictions and upper limits are set on the cross section times branching fraction sigma times B(pp to "a" to an oppositely charged muon pair) in the range of 1.5-7.5 pb. These results improve on existing bounds on the "a" b-bbar coupling for m("a") < m(Upsilon(1S)) and are the first significant limits for m("a") > m(Upsilon(3S)). Constraints on the supersymmetric parameter space are presented in the context of the next-to-minimal model.
In this work, we present a search for the possible production of Dark Matter particles at the Large Hadron Collider alongside a new hypothetical gauge boson denoted by Z$^{\prime}$, which is governed by a model called Mono-Z$^{\prime}$. The topology of the studied events is dimuons plus large missing transverse momentum. The analyzed data were the CMS open data samples collected by the CMS detector, in addition to the CMS open Monte Carlo samples, for the proton-proton collisions at 8 TeV center of mass energy during 2012, which correspond to an integrated luminosity of 11.6 fb$^{-1}$. Two ben…
Search for $t$-channel scalar and vector leptoquark exchange in the high-mass dimuon and dielectron spectra in proton-proton collisions at $\sqrt{s}$ = 13 TeV
This analysis shows a search for dark fermion particles produced in association with a heavy neutral gauge boson (Z$^{\prime}$). The studied events topology are dimuon and a large missing transverse momentum. %We considered the muonic decay of Z$^{\prime}$. The analyzed data were the Open Data collected by the CMS detector in proton-proton collisions at the LHC in 2012 and correspond to an integrated luminosity of 11.6 fb$^{-1}$ at $\sqrt{s} = $ 8 TeV. One benchmark scenario the light vector was used for interpreting the data, based on a simplified model so called the mono-Z$^{\prime}$ model. …
Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data sample recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb$^{-1}$. The differential cross section as a function of the dimuon mass is measured in the range 15-600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15-60 GeV and 60-120 GeV, and rati…
This paper presents a search for decays of the Higgs boson with a mass of 125 GeV into a pair of new pseudoscalar particles, $H\rightarrow aa$, where one $a$-boson decays into a $b$-quark pair and the other into a muon pair. The search uses 139 fb$^{-1}$ of proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13$ TeV recorded between 2015 and 2018 by the ATLAS experiment at the LHC. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at a dimuon invarian…
Forward-backward asymmetry of Drell-Yan lepton pairs in pp collisions at sqrt(s) = 7 TeV
本文测量了sqrt（s）= 7 TeV pp碰撞中Drell-Yan轻子对的前后不对称性（A[FB]）。用CMS检测器收集的数据样本对应于5个逆毫微微光垒的积分亮度。测量的不对称性作为双轻子质量和双电子和双μ子通道中的快度的函数。还介绍了两个通道的组合结果。在双μ子通道中的A[FB]测量和两个通道的组合是在强子对撞机上获得的第一个这样的结果。测量的不对称性与标准模型的预测是一致的。
Searching in CMS Open Data for Dimuon Resonances with Substantial Transverse Momentum
我们使用CMS Open Data研究了7 TeV pp碰撞中2.11/fb的双μ子事件，并寻找具有中等质量（14-66 GeV）和大量横向动量（pT）的窄双μ子共振。应用25 GeV和60 GeV的dimuon pT切割，我们探索两个重叠的样本：一个与孤立的μ子，和一个提示μ子没有隔离的要求。使用后一个样本需要关于探测器效应和QCD背景的信息，这些信息我们直接从CMS开放数据中获得。我们提出了独立于模型的限制产品的截面，分支分数，接受，和效率。这些限制是强的，相对于相应的包容性搜索没有pT削减，多达9倍。我们的“pT增强”dimuon搜索策略提供了改进的灵敏度模型，其中一个新的粒子主要是在更重的东西的衰变中产生的，例如，在希格斯玻色子或TeV级顶级伙伴的衰变中可能发生。用当前13 TeV数据实现这种方法应进一步提高对这种信号的灵敏度，大约提高一个数量级。
Exclusive dimuon production and coherent charmonium photoproduction at forward rapidity in ultra-peripheral Pb$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}}=5.36}$ TeV
European Organization for Nuclear Research（欧洲核子研究中心）
Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, $\mathrm{PbPb}(γγ) \rightarrow μ^+μ^- (\mathrm{Pb}^{(\star)}\mathrm{Pb}^{(\star)} )$, is studied using $\mathcal{L}_{\mathrm{int}} = 0.48$ nb$^{-1}$ of $\sqrt{s_\mathrm{NN}}=5.02$ TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region $p_{\mathrm{T}μ} > 4$ GeV, $|η_μ| < 2.4$, invariant mass $m_{μμ} > 10$ GeV, and $p_{\mathrm{T,μμ}} < 2$ GeV. The primary bac…
Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state of two muons and two $τ$ leptons in proton-proton collisions at $\sqrt{s}=$ 13 TeV
A search for long-lived particles decaying into muon pairs is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017 and 2018, corresponding to an integrated luminosity of 101 fb$^{-1}$. The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No si…
Charm and beauty quark production measurement represents a fundamental means to access the initial stage of hadronic collisions. Being produced almost exclusively in initial hard partonic scatterings due to their large masses, $m_{\text{c}}=$ 1.3 $ \text{GeV}/c^2$ and $m_{\text{b}} =$ 4.1 $ \text{GeV}/c^2$, charm and beauty quarks are ideal tools to investigate various QCD aspects. In addition, the corresponding measurements in pp collisions represent a baseline for cold nuclear matter studies in p--A collisions as well as for the characterization of the hot and dense interacting nuclear matte…
