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Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.4
<P>Measurements of the differential and double-differential Drell–Yan cross sections in the dielectron and dimuon channels are presented. They are based on proton–proton collision data at [FORMULA OMISSION] recorded with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7[FORMULA OMISSION]. The measured inclusive cross section in the [FORMULA OMISSION] peak region (60–120[FORMULA OMISSION]), obtained from the combination of the dielectron and dimuon channels, is [FORMULA OMISSION], where the statistical uncertainty is negligible. The differential cross section [FORMULA OMISSION] in the dilepton mass range 15–2000[FORMULA OMISSION] is measured and corrected to the full phase space. The double-differential cross section [FORMULA OMISSION] is also measured over the mass range 20 to 1500[FORMULA OMISSION] and absolute dilepton rapidity from 0 to 2.4. In addition, the ratios of the normalized differential cross sections measured at [FORMULA OMISSION] and 8[FORMULA OMISSION] are presented. These measurements are compared to the predictions of perturbative QCD at next-to-leading and next-to-next-to-leading (NNLO) orders using various sets of parton distribution functions (PDFs). The results agree with the NNLO theoretical predictions computed with <SMALL>FEWZ</SMALL> 3.1 using the CT10 NNLO and NNPDF2.1 NNLO PDFs. The measured double-differential cross section and ratio of normalized differential cross sections are sufficiently precise to constrain the proton PDFs.</P>
Search for disappearing tracks in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.1
<P>A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. Disappearing tracks are identified as those with little or no associated calorimeter energy deposits and with missing hits in the outer layers of the tracker. The search uses proton-proton collision data recorded at root s = 8 TeV that corresponds to an integrated luminosity of 19.5 fb(-1). The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking (AMSB) model. The number of observed events is in agreement with the background expectation, and limits are set on the cross section of direct electroweak chargino production in terms of the chargino mass and mean proper lifetime. At 95% confidence level, AMSB models with a chargino mass less than 260 GeV, corresponding to a mean proper lifetime of 0.2 ns, are excluded.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.1
<P>A measurement of the W boson helicity is presented, where the W boson originates from the decay of a top quark produced in pp collisions. The event selection, optimized for reconstructing a single top quark in the final state, requires exactly one isolated lepton (muon or electron) and exactly two jets, one of which is likely to originate from the hadronization of a bottom quark. The analysis is performed using data recorded at a center-of-mass energy of 8 TeV with the CMS detector at the CERN LHC in 2012. The data sample corresponds to an integrated luminosity of 19.7 fb(-1). The measured helicity fractions are F-L = 0.298 +/- 0.028 (stat) +/- 0.032(syst), F-0 = 0.720 +/- 0.039 (stat) +/- 0.037(syst), and F-R = -0.018 +/- 0.019 (stat) +/- 0.011(syst). These results are used to set limits on the real part of the tWb anomalous couplings, g(L) and g(R).</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.5
<P>Properties of the Higgs boson with mass near 125[FORMULA OMISSION] are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [FORMULA OMISSION], [FORMULA OMISSION], [FORMULA OMISSION], [FORMULA OMISSION], [FORMULA OMISSION], and [FORMULA OMISSION] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1[FORMULA OMISSION] at 7[FORMULA OMISSION] and up to 19.7[FORMULA OMISSION] at 8[FORMULA OMISSION]. From the high-resolution [FORMULA OMISSION] and [FORMULA OMISSION] channels, the mass of the Higgs boson is determined to be [FORMULA OMISSION]. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is [FORMULA OMISSION] at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.5
<P>Searches for supersymmetry (SUSY) are performed using a sample of hadronic events produced in 8 TeV pp collisions at the CERN LHC. The searches are based on the M-T2 variable, which is a measure of the transverse momentum imbalance in an event. The data were collected with the CMS detector and correspond to an integrated luminosity of 19.5 fb(-1). Two related searches are performed. The first is an inclusive search based on signal regions defined by the value of the M-T2 variable, the hadronic energy in the event, the jet multiplicity, and the number of jets identified as originating from bottom quarks. The second is a search for a mass peak corresponding to a Higgs boson decaying to a bottom quark-antiquark pair, where the Higgs boson is produced as a decay product of a SUSY particle. For both searches, the principal backgrounds are evaluated with data control samples. No significant excess over the expected number of background events is observed, and exclusion limits on various SUSY models are derived.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.7
<P>Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton–proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.7
<P>This paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7[FORMULA OMISSION] with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1[FORMULA OMISSION]. The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, <SMALL>MADGRAPH</SMALL> interfaced with <SMALL>PYTHIA6</SMALL> displays the overall best agreement with data.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.6
<P>The inclusive jet cross section for proton–proton collisions at a centre-of-mass energy of 7[FORMULA OMISSION] was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0[FORMULA OMISSION]. The measurement covers a phase space up to 2[FORMULA OMISSION] in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass [FORMULA OMISSION] is determined to be [FORMULA OMISSION], which is in agreement with the world average.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.6
<P>A search is presented for particle dark matter produced in association with a pair of top quarks in pp collisions at a centre-of-mass energy of root s = 8TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 19.7 fb(-1). This search requires the presence of one lepton, multiple jets, and large missing transverse energy. No excess of events is found above the SM expectation, and upper limits are derived on the production cross section. Interpreting the findings in the context of a scalar contact interaction between fermionic dark matter particles and top quarks, lower limits on the interaction scale are set. These limits are also interpreted in terms of the dark matter-nucleon scattering cross sections for the spin-independent scalar operator and they complement direct searches for dark matter particles in the low mass region.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,Kiesenhofer, American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.5
<P>A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) fb(-1) in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at root s TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle's mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV/c(2) decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV= c(2), each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV/c(2)), the limits are in the range 2-50 fb. These limits are sensitive to Higgs boson branching fractions as low as 10(-1).</P>