Results are presented from a search for large, extra spatial dimensions in events with either two isolated muons or two isolated electrons. The data are from proton-proton interactions at s = 7 TeV ...collected with the CMS detector at the LHC. The size of the data sample corresponds to an integrated luminosity of approximately 2 fb - 1 . The observed dimuon and dielectron mass spectra are found to be consistent with standard-model expectations. Depending on the number of extra dimensions, the 95% confidence level limits from the combined mu mu and ee channels range from M s > 2.4 TeV to M s > 3.8 TeV , where M s characterizes the scale for the onset of quantum gravity.
We present a measurement of the ratio of the decay rates Γ(KL→π+π−)/Γ(KL→π±e∓ν), denoted as ΓK2π/ΓKe3. The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the ...CERN SPS. Using a sample of 47 000 K2π and five million Ke3 decays, we find ΓK2π/ΓKe3=(4.835±0.022stat.±0.016syst.)×10−3. From this we derive the branching ratio of the CP violating decay KL→π+π− and the CP violation parameter |η+−|. Excluding the CP conserving direct photon emission component KL→π+π−γ, we obtain the results BR(KL→π+π−)=(1.941±0.019)×10−3 and |η+−|=(2.223±0.012)×10−3.
The direct CP violation parameter Re(epsilon'/epsilon) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. With 3.3 million KL->pi0pi0 ...events collected during the 1998 and 1999 running periods, a result of Re(epsilon'/epsilon) = (15.0 +- 2.7)x10-4 has been obtained. The result combined with the published 1997 sample is Re(epsilon'/epsilon) = (15.3 +- 2.6)x10-4.
The KS→π+π−e+e− decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k KS→π+π−e+e− events and 59 k KL→π+π−πD0 normalization decays, the KS→π+π−e+e− ...branching ratio relative to the KL→π+π−πD0 one was determined to be BR(KS→π+π−e+e−)/BR(KL→π+π−πD0)=(3.28±0.06stat±0.04syst)×10−2. This result was used to set the upper limit |gE1/gBR|<3.0 at 90% CL on the presence, in the decay amplitude, of an E1 direct emission (gE1) term relative to the dominant inner bremsstrahlung (gBR) term. The CP-violating asymmetry Aϕ in the sinϕcosϕ distribution of KS→π+π−e+e− events, where ϕ is the angle between the π+π− and the e+e− decay planes in the kaon centre of mass, was found to be Aϕ=(−0.4±0.8)%, consistent with zero. These results are in good agreement with a description of the KS→π+π−e+e− decay amplitude dominated by the CP-even inner bremsstrahlung process.
The decay asymmetries of the weak radiative hyperon decays Xi super(0)--> g and Xi super(0)-->sigma super(0)g have been measured with high precision using data of the NA48/1 experiment at CERN. From ...about 52 000 Xi super(0)--> g and 15 000 Xi super(0)-->sigma super(0)g decays, we obtain for the decay asymmetries a sub()Xiu0-> g-0.704+/-0.019 sub(stat)+/- 0.064 sub(syst) and a sub()Xiu0->sigma super(0)g-0.729+/-0.030 sub(s)tat/-0.076 sub(syst), respectively. These results are in good agreement with previous experiments, but more precise.
Using the full data set of the NA48/2 experiment, the decay K±→π±e+e−γ is observed for the first time, selecting 120 candidates with 7.3±1.7 estimated background events. With K±→π±πD0 as ...normalisation channel, the branching ratio is determined in a model-independent way to be Br(K±→π±e+e−γ,meeγ>260 MeV/c2)=(1.19±0.12stat±0.04syst)×10−8. This measured value and the spectrum of the e+e−γ invariant mass allow a comparison with predictions of chiral perturbation theory.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Results are presented from a search for the electroweak production of supersymmetric particles in pp collisions in final ...states with two tau leptons. The data sample corresponds to an integrated luminosity between 18.1 fb super(-1) and 19.6 fb super(-1) depending on the final state of tau lepton decays, at ... TeV, collected by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with the expected standard model backgrounds. The results are interpreted using simplified models describing the pair production and decays of charginos or tau sleptons. For models describing the pair production of the lightest chargino, exclusion regions are obtained in the plane of chargino mass vs. neutralino mass under the following assumptions: the chargino decays into third-generation sleptons, which are taken to be the lightest sleptons, and the sleptons masses lie midway between those of the chargino and the neutralino. Chargino masses below 420 GeV are excluded at a 95% confidence level in the limit of a massless neutralino, and for neutralino masses up to 100 GeV, chargino masses up to 325 GeV are excluded at 95% confidence level. Constraints are also placed on the cross section for pair production of tau sleptons as a function of mass, assuming a massless neutralino. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Cross sections for the production of a Z boson in association with jets in proton-proton collisions at a centre-of-mass ...energy of ... TeV are measured using a data sample collected by the CMS experiment at the LHC corresponding to 19.6 fb super(-1). Differential cross sections are presented as functions of up to three observables that describe the jet kinematics and the jet activity. Correlations between the azimuthal directions and the rapidities of the jets and the Z boson are studied in detail. The predictions of a number of multileg generators with leading or next-to-leading order accuracy are compared with the measurements. The comparison shows the importance of including multi-parton contributions in the matrix elements and the improvement in the predictions when next-to-leading order terms are included. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The spectra of charged particles produced within the pseudorapidity window | eta | < 1 at ... TeV are measured using 404 mu ...b super(-1) of PbPb and 27.4 pb super(-1) of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < p sub(T) < 400 GeV in pp and 0.7 < p sub(T) < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R sub(AA), is measured in bins of collision centrality. The R sub(AA) in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the p sub(T) region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest p sub(T) measured, and approaches unity in the vicinity of p sub(T) = 200 GeV. The R sub(AA) is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, R sub(pA), up to 120 GeV. For p sub(T) > 20 GeV, R sub(pA) exhibits weak momentum dependence and shows a moderate enhancement above unity. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of the double-differential inclusive jet cross section as a function of the jet transverse momentum p sub(T) ...and the absolute jet rapidity |y| is presented. Data from LHC proton-proton collisions at ... TeV, corresponding to an integrated luminosity of 19.7 fb super(-1), have been collected with the CMS detector. Jets are reconstructed using the anti-k sub(T) clustering algorithm with a size parameter of 0.7 in a phase space region covering jet p sub(T) from 74 GeV up to 2.5 TeV and jet absolute rapidity up to |y| = 3.0. The low-p sub(T) jet range between 21 and 74 GeV is also studied up to |y| = 4.7, using a dedicated data sample corresponding to an integrated luminosity of 5.6 pb super(-1). The measured jet cross section is corrected for detector effects and compared with the predictions from perturbative QCD at next-to-leading order (NLO) using various sets of parton distribution functions (PDF). Cross section ratios to the corresponding measurements performed at 2.76 and 7 TeV are presented. From the measured double-differential jet cross section, the value of the strong coupling constant evaluated at the Z mass is alpha sub(S)(M sub(Z))=0.1164 sub(-0.0043) super(+0.0060), where the errors include the PDF, scale, nonperturbative effects and experimental uncertainties, using the CT10 NLO PDFs. Improved constraints on PDFs based on the inclusive jet cross section measurement are presented. Figure not available: see fulltext.
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