Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at root s=13 TeV

A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at s&radic; = 13 TeV collected in the three-year period 2016&ndash;2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb&minus;1. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on &chi;&sim;02/&chi;&sim;&plusmn;1 masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter &mu; up to 180 GeV with the bino mass parameter M1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.</p

Study of dijet events with large rapidity separation in proton-proton collisions at root s=2.76 TeV

The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at s&radic; = 2.76 TeV for jets with transverse momentum pT &gt; 35 GeV and rapidity |y| &lt; 4.7. Various dijet production cross section ratios are also measured. A veto on additional jets with pT &gt; 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.</p

Measurements of the associated production of a W boson and a charm quark in proton-proton collisions at √s=8TeV

Measurements of the associated production of aW boson and a charm (c) quark in proton&ndash;proton collisionsat a centre-of-mass energy of 8 TeV are reported. The anal-ysis uses a data sample corresponding to a total integratedluminosity of 19.7 fb&minus;1 collected by the CMS detector atthe LHC. The W bosons are identified through their leptonicdecays to an electron or a muon, and a neutrino. Charm quarkjets are selected using distinctive signatures of charm hadrondecays. The product of the cross section and branching frac-tion &sigma; (pp &rarr; W + c + X)B(W &rarr; �&nu;), where � = e or &mu;,and the cross section ratio &sigma; (pp &rarr; W+ + &macr;c + X)/&sigma; (pp &rarr;W&minus; + c + X) are measured in a fiducial volume and differ-entially as functions of the pseudorapidity and of the trans-verse momentum of the lepton from the W boson decay. Theresults are compared with theoretical predictions. The impactof these measurements on the determination of the strangequark distribution is assessed.</p

Search for low-mass dilepton resonances in Higgs boson decays to four-lepton final states in proton-proton collisions at root s=13 TeV

A search for low-mass dilepton resonances in Higgs boson decays is conducted in the four-lepton final state. The decay is assumed to proceed via a pair of beyond the standard model particles, or one such particle and a Z boson. The search uses proton&ndash;proton collision data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 137fb&minus;1, at a center-of-mass energy s&radic;=13TeV. No significant deviation from the standard model expectation is observed. Upper limits at 95% confidence level are set on model-independent Higgs boson decay branching fractions. Additionally, limits on dark photon and axion-like particle production, based on two specific models, are reported.</p

Observation of B-0 ->psi(2S)K-S(0)pi(+)pi(-) and B-s(0)->psi(2S)K-S(0) decays

Using a data sample of &radic;s = 13 TeV proton-proton collisions collected by the CMS experiment atthe LHC in 2017 and 2018 with an integrated lumi-nosity of 103 fb&minus;1 , the B0s &rarr; &psi;(2S)K0S and B 0 &rarr;&psi;(2S)K0S&pi;+&pi;&minus; decays are observed with significancesexceeding 5 standard deviations. The resulting branch-ing fraction ratios, measured for the first time, corre-spond to B(B0s &rarr; &psi;(2S)K 0S )/B(B0 &rarr; &psi;(2S)K 0S ) =(3.33 &plusmn; 0.69(stat) &plusmn; 0.11 (syst) &plusmn; 0.34 ( fs/ fd)) &times; 10&minus;2and B(B0 &rarr; &psi;(2S)K0S&pi;+&pi;&minus;)/B(B0 &rarr; &psi;(2S)K0S) =0.480 &plusmn; 0.013 (stat) &plusmn; 0.032 (syst), where the last uncer-tainty in the first ratio is related to the uncertainty in the ratioof production cross sections of B 0s and B 0 mesons, fs/ fd</p

Nuclear modification of Y states in pPb collisions at root S-NN=5.02 TeV

Production cross sections of &Upsilon;(1S), &Upsilon;(2S), and &Upsilon;(3S) states decaying into &mu;+&mu;&minus; in proton-lead (pPb)collisions are reported using data collected by the CMS experiment at &radic;sNN = 5.02 TeV. A comparison ismade with corresponding cross sections obtained with pp data measured at the same collision energyand scaled by the Pb nucleus mass number. The nuclear modification factor for &Upsilon;(1S) is found to beRpPb(&Upsilon;(1S)) = 0.806 &plusmn;0.024 (stat)&plusmn;0.059 (syst). Similar results for the excited states indicate a sequentialsuppression pattern, such that RpPb(&Upsilon;(1S)) &gt; RpPb(&Upsilon;(2S)) &gt; RpPb(&Upsilon;(3S)). The suppression of all states ismuch less pronounced in pPb than in PbPb collisions, and independent of transverse momentum p&Upsilon;T andcenter-of-mass rapidity y&Upsilon;CM of the individual &Upsilon; state in the studied range p&Upsilon;T &lt; 30 GeV/c and |y&Upsilon;CM| &lt;1.93. Models that incorporate final-state effects of bottomonia in pPb collisions are in better agreementwith the data than those which only assume initial-state modifications.</p

Measurement of the Inclusive Semi-electronic D0D^0 Branching Fraction

Using the angular correlation between the $\pi^+$ emitted in a $D^{*+} \rightarrow D^0 \pi^+$ decay and the $e^+$ emitted in the subsequent $D^0 \rightarrow Xe^+\nu$ decay, we have measured the branching fraction for the inclusive semi-electronic decay of the $D^0$ meson to be: {\cal B}(D^0 \rightarrow X e^+ \nu) = [6.64 \pm 0.18 (stat.) \pm 0.29 (syst.)] \%. The result is based on 1.7 fb$^{-1}$ of $e^+e^-$ collisions recorded by the CLEO II detector located at the Cornell Electron Storage Ring (CESR). Combining the analysis presented in this paper with previous CLEO results we find, \frac{{\cal B} (D^0 \rightarrow X e^+ \nu)} {{\cal B} (D^0 \rightarrow K^- \pi^+)} = 1.684 \pm 0.056 (stat.) \pm 0.093(syst.) and \frac{{\cal B}(D\rightarrow K^-e^+\nu)} {{\cal B}(D\rightarrow Xe^+\nu)} = 0.581 \pm 0.023 (stat.) \pm 0.028(syst.). The difference between the inclusive rate and the sum of the measured exclusive branching fractions (measured at CLEO and other experiments) is $(3.3 \pm 7.2) \%$ of the inclusive rate.Comment: Latex file, 33pages, 4 figures Submitted to PR

Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

X-ray emission from the Sombrero galaxy: discrete sources

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30 kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-low indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC LF at fainter luminosities down to 1E35 erg/s. The derived index rules out a faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres