Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million ...collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, η, and full azimuth, ϕ, as a function of charged particle multiplicity and particle transverse momentum, pT. In high-multiplicity events, a long-range (2<|Δη|<4), near-side (Δϕ≈0) structure emerges in the two-particle Δη–Δϕ correlation functions. This is the first observation of such correlations in proton–nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at s=7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of pT=1–1.5 GeV/c and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions.
Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the ...CMS detector over a broad range of pseudorapidity (
η
) and azimuthal angle (
ϕ
). Short-range correlations in Δ
η
, which are studied in minimum bias events, are characterized using a simple “independent cluster” parametrization in order to quantify their strength (cluster size) and their extent in
η
(cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb
−1
data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate
p
T
of 1–3 GeV/
c
, 2.0 < |Δ
η
| < 4
.
8 and Δ
ϕ
≈ 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in
pp
or
collisions.
A
bstract
A search for a heavy Higgs boson in the H → WW and H → ZZ decay channels is reported. The search is based upon proton-proton collision data samples corresponding to an integrated luminosity ...of up to 5.1 fb
−1
at
s
=
7
TeV and up to 19.7fb
−1
at
s
=
8
TeV, recorded by the CMS experiment at the CERN LHC. Several final states of the H → WW and H → ZZ decays are analyzed. The combined upper limit at the 95% confidence level on the product of the cross section and branching fraction exclude a Higgs boson with standard model-like couplings and decays in the range 145 <
m
H
< 1000 GeV. We also interpret the results in the context of an electroweak singlet extension of the standard model.
A model-independent search for a narrow resonance produced in proton-proton collisions at sqrt(s) = 8 TeV and decaying to a pair of 125 GeV Higgs bosons that in turn each decays into bottom ...quark-antiquark pairs is performed by the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 17.9 inverse femtobarns. No evidence for a signal is observed. Upper limits at a 95% confidence level on the production cross section for such a resonance, in the mass range from 270 to 1100 GeV, are reported. Using these results, a radion with decay constant of 1 TeV and mass from 300 to 1100 GeV, and a Kaluza-Klein graviton with mass from 380 to 830 GeV are excluded at a 95% confidence level.
Constraints are presented on the total width of the recently discovered Higgs boson, ΓH, using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson ...decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb−1 at a center-of-mass energy s=7 TeV and 19.7 fb−1 at s=8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of ΓH<22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of mH=125.6 GeV.
Measurements of two-particle angular correlations between an identified strange hadron (KS0 or Λ/Λ‾) and a charged particle, emitted in pPb collisions, are presented over a wide range in ...pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 35 nb−1, were collected at a nucleon–nucleon center-of-mass energy (sNN) of 5.02 TeV with the CMS detector at the LHC. The results are compared to semi-peripheral PbPb collision data at sNN=2.76 TeV, covering similar charged-particle multiplicities in the events. The observed azimuthal correlations at large relative pseudorapidity are used to extract the second-order (v2) and third-order (v3) anisotropy harmonics of KS0 and Λ/Λ‾ particles. These quantities are studied as a function of the charged-particle multiplicity in the event and the transverse momentum of the particles. For high-multiplicity pPb events, a clear particle species dependence of v2 and v3 is observed. For pT<2 GeV, the v2 and v3 values of KS0 particles are larger than those of Λ/Λ‾ particles at the same pT. This splitting effect between two particle species is found to be stronger in pPb than in PbPb collisions in the same multiplicity range. When divided by the number of constituent quarks and compared at the same transverse kinetic energy per quark, both v2 and v3 for KS0 particles are observed to be consistent with those for Λ/Λ‾ particles at the 10% level in pPb collisions. This consistency extends over a wide range of particle transverse kinetic energy and event multiplicities.
A search for narrow resonances with a mass of at least 1 TeV in the dijet mass spectrum is performed using pp collisions at s=7 TeV corresponding to an integrated luminosity of 1 fb−1, collected by ...the CMS experiment at the LHC. No resonances are observed. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark–quark, quark–gluon, and gluon–gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances with mass less than 4.00 TeV, E6 diquarks with mass less than 3.52 TeV, excited quarks with mass less than 2.49 TeV, axigluons and colorons with mass less than 2.47 TeV, and W′ bosons with mass less than 1.51 TeV. These results extend previous exclusions from the dijet mass search technique.
A
bstract
Invariant mass spectra for jets reconstructed using the anti-
k
T
and CambridgeAachen algorithms are studied for different jet “grooming” techniques in data corresponding to an integrated ...luminosity of 5 fb
−1
, recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation.
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