C. Royon
We describe the most recent results from the Proton Precision Spectrometer from the CMS and TOTEM collaborations, namely the first observation of exclusive di-lepton production at high mass at the LHC, and the prospects concerning the sensitivity to quartic anomalous couplings..
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Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer
本文介绍了 CMS-TOTEM 精确质子谱仪（PPS）在 LHC Run 2 期间收集的数据，详细阐述了其准直、光学校准、质子重建程序及模拟性能，并通过双轻子事件验证了重建与模拟，证明了高亮度对撞机近束质子谱仪连续运行的可行性。
Exclusive and diffractive physics measurements are important for the better understanding of the non-perturbative regime of QCD. Two recent results of the CMS experiment is presented in this paper. The total and differential cross sections of central exclusive $π^+π^-$ production are measured at 5.02 and 13 TeV in the $p_{\mathrm{T}}(π) > 0.2~$GeV/$c$ and $|η(π)| < 2.4$ kinematic region. The invariant mass distribution is fitted by the sum of a continuum and four interfering relativistic Breit-Wigner functions. In the second part of the paper the measurement of the single diffractive dijets is…
This note highlights the predictive power of the 3-component Pomeron model designed by the authors ten years ago with a partial account of the multiplicity of Pomerons in QCD. The model is put to the test by comparing its predictions with the recent data from DO and TOTEM Collaborations at 1.96 and 7 TeV, respectively. We also compare model predictions for inelastic cross section to experimental measurement by TOTEM, CMS, ALICE, and ATLAS collaborations. It is shown that the DO data are perfectly predicted by the model. Total, elastic, and inelastic cross section predictions are in agreement w…
The CMS+TOTEM Precision Proton Spectrometer operated for the first time in 2016, collecting data during $pp$ collisions at $\sqrt{s} = 13$ TeV at the CERN Large Hadron Collider. Procedures for the detector alignment, optics corrections, and background estimations were developed, and applied to an analysis of the process $pp \rightarrow p μ^{+}μ^{-} p^{(*)}$ with dimuon masses larger than 110 GeV. A total of 12 candidate events are observed, corresponding to an excess of $>4σ$ over the background prediction. This constitutes the first evidence for this process at such masses, and demonstrates t…
A search for central exclusive production of top quark pairs ($\mathrm{t}\bar{\mathrm{t}}$) is presented using collision data collected by CMS and the CMS-TOTEM Precision Proton Spectrometer in 2017. A data-driven method to estimate the background from coincidences of inclusive events and pileup protons is described, as well as the development of a Boosted Decision Tree classifier to separate the exclusive $\mathrm{t}\bar{\mathrm{t}}$ signal from the inclusive $\mathrm{t}\bar{\mathrm{t}}$ background. The first-ever upper limits on the cross section of exclusive $\mathrm{t}\bar{\mathrm{t}}$ are…
We analyze the problem of correlating pp interaction data from the central detectors with a subevent measured in an independent system of leading proton detectors using FP420 as an example. FP420 is an R&D project conducted by a collaboration formed by members of ATLAS and CMS to investigate the possibility of detecting new physics in the central exclusive channel, PP -> P + X + P,where the central system X may be a single particle, for example a Standard Model Higgs boson. With standard LHC optics, the protons emerge from the beam at a distance of 420m from the Interaction Point, for M_X ~ 12…
A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
本文利用CMS探测器和CMS-TOTEM精密质子谱仪，通过丢失质量技术在13 TeV质子-质子碰撞中搜索Z/γ与大质量粒子X的伴随产生，未发现显著超出并设定了模型无关的截面上限。
The TOTEM experiment with its detectors in the forward region of CMS and the Roman Pots along the beam line will determine the total pp cross-section via the optical theorem by measuring both the elastic cross-section and the total inelastic rate. TOTEM will have dedicated runs with special high-beta* beam optics and a reduced number of proton bunches resulting in a low effective luminosity between 1.6 x 10^{28} cm^{-2} s^{-1} and 2.4 x 10^{29} cm^{-2} s^{-1}. In these special conditions also an absolute luminosity measurement will be made, allowing the calibration of the CMS luminosity monito…
Pseudorapidity (eta) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges abs(eta) < 2.2 and 5.3 < abs(eta) < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of 45 inverse microbarns. Measurements are presented for three event categories. The most inclusive category is sensitive to 91-96% of the total inelastic proton-proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single d…
Photon induced processes can be used as a sensitive probe of new physics searches and can be studied using exclusive processes. These processes lead to unprecedented sensitivities on quartic anomalous couplings between photons and W and Z bosons, and new physics searches. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to select exclusive processes. PPS is designed to operate in standard high-luminosity runs at the LHC to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive proc…
We describe the reaches on quartic $γγγγ$, $γγWW$, $γγZZ$, $γγγZ$, $γγt \bar{t}$ anomalous couplings at the LHC using intact protons in the final state measured in AFP in ATLAS or PPS in CMS-TOTEM.
Recent results in soft QCD at LHC by the ATLAS, CMS and TOTEM Collaborations are presented. Special focus is reserved to studies in diffractive and forward physics, and to the underlying event, with comparison with previous results and highlighting novel techniques.
The process pp$\to\ell^+\ell^-$p$^{(*)}$, with $\ell^+\ell^-$ a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $\sqrt{s} =$ 13 TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p$^{*}$, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb$^{-1}$ collected during standard…
Recent CMS results on diffraction are presented. These include the measurements of the soft diffractive cross sections, of the forward rapidity gap cross section, of the diffractive dijet cross section, the measurement of a large rapidity gap in W and Z boson events and the measurement of the pseudorapidity distribution of charged particles in a single diffractive enhanced sample. This last measurement is the first common result of the CMS and TOTEM collaborations. Some prospects of common CMS-TOTEM data taking are also discussed.
We describe recent results from CMS and TOTEM on hard diffraction, diffractive jets and jet gap jet events. We also give the first sensitivities and limits on quartic anomalous couplings and axion-like particles at high mass using the LHC as a $γγ$ collider. The predicted sensitivities with 300 fb$^{-1}$ are better by two or three orders of magnitude compared to the more standard methods at the LHC without measuring intact protons after collision
In this talk we present a selection of forward physics results recently obtained with the run-1 and run-2 LHC data by the CMS, LHCf and TOTEM experiments. The status of the very forward LHC proton spectrometer, CT-PPS, is discussed: emphasis is given to the physics potential of CT-PPS and to the analyses that are currently ongoing with the data collected in 2016. Very recent forward measurements obtained with the LHCf and the CMS-CASTOR calorimeter are then addressed. In particular, CMS measured the inclusive energy spectrum in the very forward direction for proton-proton collisions at a cente…
We present the project to install new forward proton detectors in the CMS and ATLAS experiments called PPS and AFP respectively.
At the LHC, diffractive physics will be explored by the dedicated experiment TOTEM whose Technical Design Report has been approved in Summer 2004. The experimental programme will be carried out partly in TOTEM standalone mode for purely forward phenomena like elastic scattering, and partly in collaboration with CMS for processes requiring a full rapidity coverage. ATLAS and ALICE are interested in diffraction for a later stage. This article presents the TOTEM/CMS running scenario for diffractive physics in the first year of LHC. We discuss which processes are within reach and with which statis…
Central exclusive production in CMS+TOTEM
本文利用 CMS+TOTEM 在 13 TeV 特殊高-$β^*$ 运行数据研究 pp 碰撞中带电强子对的中心排他产生，测量了微分截面并首次观测到双质子方位角分布的抛物线极小值，通过模型调谐确定了坡密子相关的多种物理量。
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $ξ$ and the four-momentum transfer squared $t$. Both processes pp$\to$pX and pp$\to$Xp, ie with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at $\sqrt{s}$= 8 TeV during a dedicated run with $β^{\as…
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Ψ$, $Ψ(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
The CMS/TOTEM and ATLAS collaborations carry out a program of forward physics with several near-beam detectors extending their coverage to high pseudorapidities. This instrumentation includes calorimeters (CASTOR and ZDC), tracking devices (TOTEM T1 and T2), proton taggers (Roman Pots and FP420), and instrumentation dedicated to luminosity monitoring and normalisation. A rich physics program is accessible, including soft QCD interactions, Diffraction, photon-induced physics and luminosity measurements.
We describe the most recent results at the Large Hadron Collider from the ALICE, ATLAS, CMS, LHCb and TOTEM experiments concerning the elastic, inelastic and total cross section measurements as well as particle production in soft and hard processes.
We present recent results on Minimum Bias, MPI and DPS, Diffractive and Exclusive studies using data collected during Run 1 of the LHC. The measurements include data collected in pp collisions at $\sqrt s = 7$, and $8$ TeV by the CMS Collaboration. Double parton scattering is investigated in several final states including vector bosons and jets, and the effective cross section results are compared to other experiments and to MPI models tuned to recent underlying event measurements at CMS. Inclusive diffractive cross sections are discussed and compared to models, while searches and measurements…
Exclusive dilepton production occurs with high cross section in gamma-mediated processes at the LHC. The pure QED process $γγ\rightarrow\ell^+\ell^-$ provides the conditions to study particle production with masses at the electroweak scale. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to selecting exclusive processes. PPS is a detector system to add tracking and timing information at approximately 210~m from the interaction point around the CMS detector. It is designed to operate at high luminosity with up to…
The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM wi…
The CMS Collaboration intends to pursue the study of central exclusive production (CEP) events, pp $\to$ pXp, at the High-Luminosity LHC (HL-LHC) by means of a new near-beam proton spectrometer. In CEP events, the state X is produced at central rapidities, and the scattered protons do not leave the beam pipe. The kinematics of X can be fully reconstructed from that of the protons, which gives access to final states otherwise not visible. CEP allows unique sensitivity to physics beyond the standard model, e.g. in the search for anomalous quartic gauge couplings, axion-like particles, and in gen…
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at $\sqrt{s} = 7 $ TeV in special runs with the Roman Pot detectors placed as close to the outgoing beam as seven times the transverse beam size. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.
This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with abou…
Search for high-mass exclusive diphoton production with tagged protons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
本研究利用CMS与TOTEM的PPS探测器在13 TeV质子对撞数据中搜索高质量遍举双光子产生，观测到1个候选事件（预期本底1.1个），给出了四光子反常耦合参数限制及类轴子粒子产生上限。
Search for central exclusive production of top quark pairs in proton-proton collisions at $\sqrt{s}$ = 13 TeV with tagged protons
本研究首次在LHC 13 TeV质子-质子碰撞中利用质子标记技术寻找顶夸克对的中心遍举产生，通过CMS探测器与CMS-TOTEM谱仪测量，在95%置信水平下设定了该过程产生截面的观测上限0.59 pb、预期上限1.14 pb。
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