(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Double parton scattering is investigated in proton-proton collisions at ... = 7 TeV where the final state includes ...a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 fb^sup -1^, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W + 2-jet events due to double parton scattering is measured to be 0.055 ± 0.002 (stat.) ± 0.014 (syst.). The effective cross section, sigma ^sub eff^, characterizing the effective transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 ± 0.8(stat.) ± 6.6(syst.)mb. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at ...=2.76TeV by the ...CMS collaboration, using data from the 2011 LHC heavy-ion run. The data set includes a sample of ultra-central (0-0.2% centrality) PbPb events collected using a trigger based on total transverse energy in the hadron forward calorimeters and the total multiplicity of pixel clusters in the silicon pixel tracker. A total of about 1.8 million ultra-central events were recorded, corresponding to an integrated luminosity of 120 mub-1. The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The single-particle anisotropy Fourier harmonics, from v ^sub 2^ to v ^sub 6^, are extracted as a function of particle transverse momentum. At higher transverse momentum, the v ^sub 2^ harmonic becomes significantly smaller than the higher-order v ^sub n^ (ngreater than or equal to3). The p ^sub T^-averaged v ^sub 2^ and v ^sub 3^ are found to be equal within 2%, while higher-order v ^sub n^ decrease as n increases. The breakdown of factorization of dihadron correlations into single-particle azimuthal anisotropies is observed. This effect is found to be most prominent in the ultra-central PbPb collisions, where the initial-state fluctuations play a dominant role. A comparison of the factorization data to hydrodynamic predictions with event-by-event fluctuating initial conditions is also presented. Figure not available: see fulltext.
Measurement of the Λ c + Lifetime Abudinén, F.; Aggarwal, L.; Aihara, H. ...
Physical review letters,
02/2023, Letnik:
130, Številka:
7
Journal Article
Recenzirano
Odprti dostop
An absolute measurement of the $\Lambda^{+}_c$ lifetime is reported using $\Lambda_c^+\rightarrow pK^-\pi^+$ decays in events reconstructed from data collected by the Belle II experiment at the ...SuperKEKB asymmetric-energy electron-positron collider. The total integrated luminosity of the data sample, which was collected at center-of-mass energies at or near the $\Upsilon(4S)$ resonance, is $207.2~\mbox{fb}^{-1}$. The result, $\tau(\Lambda^{+}_c) = 203.20 \pm 0.89 \,\mathrm{(stat)} \pm 0.77 \,\mathrm{(syst)}$ fs, is the most precise measurement to date and is consistent with previous determinations.
A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $H → c\bar{c}$, produced in association with a leptonically decaying $V (W \text{or} Z)$ boson is presented. The ...search is performed with proton-proton collisions at $\sqrt{s}=13\,\text {TeV}$ collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb-1. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for $Z → c\bar{c}$ in $VZ$ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on $σ(VH)\mathscr{B}(H → c\bar{c}$) is 0.94 (0.50$^{+0.22}_{– 0.15}$)pb at 95% confidence level (C.L.), corresponding to 14 (7.6$^{+3.4}_{–2.3}$) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, $κ_c$, the observed (expected) 95% C.L. interval is 1.1 < |$κ_c$| < 5.5 (|$κ_c$| < 3.4), the most stringent constraint to date.
A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 ...fb(-1) and was collected at sqrts = 8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Measurements are presented of the associated production of a W boson and a charm-quark jet (W + c) in pp ...collisions at a center-of-mass energy of 7 TeV. The analysis is conducted with a data sample corresponding to a total integrated luminosity of 5 fb^sup -1^, collected by the CMS detector at the LHC. W boson candidates are identified by their decay into a charged lepton (muon or electron) and a neutrino. The W + c measurements are performed for charm-quark jets in the kinematic region ... > 25 GeV, |eta^sup jet^| < 2.5, for two different thresholds for the transverse momentum of the lepton from the W-boson decay, and in the pseudorapidity range |eta^sup ^| < 2.1. Hadronic and inclusive semileptonic decays of charm hadrons are used to measure the following total cross sections: sigma(pp arrow right W + c + X) × ...(W arrow right ν) = 107.7 ± 3.3 (stat.) ± 6.9 (syst.) pb (... > 25 GeV) and sigma(pp arrow right W + c + X)×...(W arrow right ν) = 84.1 ± 2.0 (stat.) ± 4.9 (syst.) pb (... > 35 GeV), and the cross section ratios sigma(pp arrow right W^sup +^ + ... + X)/sigma(pp arrow right W^sup -^ + c + X) = 0.954 ± 0.025 (stat.) ± 0.004 (syst.) (... > 25 GeV) and sigma(pp arrow right W^sup +^ + ... + X)/sigma(pp arrow right W^sup -^ + c + X) = 0.938 ± 0.019 (stat.) ± 0.006 (syst.) (... > 35 GeV). Cross sections and cross section ratios are also measured differentially with respect to the absolute value of the pseudorapidity of the lepton from the W-boson decay. These are the first measurements from the LHC directly sensitive to the strange quark and antiquark content of the proton. Results are compared with theoretical predictions and are consistent with the predictions based on global fits of parton distribution functions. Figure not available: see fulltext.
The first search for scalar leptoquarks produced in τ-lepton-quark collisions is presented. It is based on a set of proton-proton collision data recorded with the CMS detector at the LHC at a ...center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb^{-1}. The reconstructed final state consists of a jet, significant missing transverse momentum, and a τ lepton reconstructed through its hadronic or leptonic decays. Limits are set on the product of the leptoquark production cross section and branching fraction and interpreted as exclusions in the plane of the leptoquark mass and the leptoquark-τ-quark coupling strength.
Results are presented from a search for new physics in the final state containing a photon (γ) and missing transverse energy (Ecombininb /(T)). The data correspond to an integrated luminosity of 5.0 ...fb(-1) collected in pp collisions at √s=7 TeV by the CMS experiment. The observed event yield agrees with standard-model expectations for the γ+Ecombininb /(T) events. Using models for the production of dark-matter particles (χ), we set 90% confidence level (C.L.) upper limits of 13.6-15.4 fb on χ production in the γ+Ecombininb /(T) state. These provide the most sensitive upper limits for spin-dependent χ-nucleon scattering for χ masses (M(χ)) between 1 and 100 GeV. For spin-independent contributions, the present limits are extended to M(χ)<3.5 GeV. For models with 3-6 large extra dimensions, our data exclude extra-dimensional Planck scales between 1.64 and 1.73 TeV at 95% C.L.
We report the first search for a nonstandard-model resonance decaying into τ pairs in e^{+}e^{-}→μ^{+}μ^{-}τ^{+}τ^{-} events in the 3.6-10 GeV/c^{2} mass range. We use a 62.8 fb^{-1} sample of ...e^{+}e^{-} collisions collected at a center-of-mass energy of 10.58 GeV by the Belle II experiment at the SuperKEKB collider. The analysis probes three different models predicting a spin-1 particle coupling only to the heavier lepton families, a Higgs-like spin-0 particle that couples preferentially to charged leptons (leptophilic scalar), and an axionlike particle, respectively. We observe no evidence for a signal and set exclusion limits at 90% confidence level on the product of cross section and branching fraction into τ pairs, ranging from 0.7 to 24 fb, and on the couplings of these processes. We obtain world-leading constraints on the couplings for the leptophilic scalar model for masses above 6.5 GeV/c^{2} and for the axionlike particle model over the entire mass range.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Measurements of the differential and double-differential Drell-Yan cross sections are presented using an ...integrated luminosity of 4.5 (4.8) fb^sup -1^ in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at ... = 7 TeV. The measured inclusive cross section in the Z-peak region (60-120 GeV) is sigma() = 986.4±0.6 (stat.)±5.9 (exp. syst.)±21.7 (th. syst.)±21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections dsigma/dm for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section d^sup 2^sigma/dm d|y| in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading orders using various sets of parton distribution functions. Figure not available: see fulltext.
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