Dijet production in PbPb collisions at a nucleon–nucleon center-of-mass energy of 2.76 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 150 ...μb−1 is analyzed. Jets are reconstructed using combined information from tracking and calorimetry, using the anti-kT algorithm with R=0.3. The dijet momentum balance and angular correlations are studied as a function of collision centrality and leading jet transverse momentum. For the most peripheral PbPb collisions, good agreement of the dijet momentum balance distributions with pp data and reference calculations at the same collision energy is found, while more central collisions show a strong imbalance of leading and subleading jet transverse momenta attributed to the jet-quenching effect. The dijets in central collisions are found to be more unbalanced than the reference, for leading jet transverse momenta up to the highest values studied.
The polarizations of prompt J/ψ and ψ(2S) mesons are measured in proton–proton collisions at s=7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an ...integrated luminosity of 4.9 fb−1. The prompt J/ψ and ψ(2S) polarization parameters λϑ, λφ, and λϑφ, as well as the frame-invariant quantity λ˜, are measured from the dimuon decay angular distributions in three different polarization frames. The J/ψ results are obtained in the transverse momentum range 14<pT<70 GeV, in the rapidity intervals |y|<0.6 and 0.6<|y|<1.2. The corresponding ψ(2S) results cover 14<pT<50 GeV and include a third rapidity bin, 1.2<|y|<1.5. No evidence of large polarizations is seen in these kinematic regions, which extend much beyond those previously explored.
Combination of CDF and D0 W -Boson mass measurements Agnew, J. P.; Annovi, A.; Bandurin, D. V. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
09/2013, Letnik:
88, Številka:
5
Journal Article
Recenzirano
Odprti dostop
We summarize and combine direct measurements of the mass of the W boson in radicals = 1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. ...Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb super(-1) of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb super(-1) of integrated luminosity. The resulting Tevatron average for the mass of the W boson is MW = 80387 + or - 16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of MW = 80385 + or - 15 MeV.
A
bstract
A search is reported for massive resonances decaying into a quark and a vector boson (W or Z), or two vector bosons (WW, WZ, or ZZ). The analysis is performed on an inclusive sample of ...multijet events corresponding to an integrated luminosity of 19.7 fb
−1
, collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. The search uses novel jet-substructure identification techniques that provide sensitivity to the presence of highly boosted vector bosons decaying into a pair of quarks. Exclusion limits are set at a confidence level of 95% on the production of: (i) excited quark resonances q
*
decaying to qW and qZ for masses less than 3.2 TeV and 2.9 TeV, respectively, (ii) a Randall-Sundrum graviton G
RS
decaying into WW for masses below 1.2 TeV, and (iii) a heavy partner of the W boson W
′
decaying into WZ for masses less than 1.7 TeV. For the first time mass limits are set on W
′
→ WZ and G
RS
→ WW in the all-jets final state. The mass limits on q
*
→ qW, q
*
→ qZ, W
′
→ WZ, G
RS
→ WW are the most stringent to date. A model with a “bulk” graviton G
bulk
that decays into WW or ZZ bosons is also studied.
Results are presented of a search for heavy particles decaying into two photons. The analysis is based on a 19.7fb-1 sample of proton–proton collisions at $\sqrt{s}$ = 8 TeV collected with the CMS ...detector at the CERN LHC. The diphoton mass spectrum from 150 to 850 GeV is used to search for an excess of events over the background. The search is extended to new resonances with natural widths of up to 10% of the mass value. No evidence for new particle production is observed and limits at 95% confidence level on the production cross section times branching fraction to diphotons are determined. These limits are interpreted in terms of two-Higgs-doublet model parameters.
A search for heavy, right-handed neutrinos,
N
ℓ
(
ℓ
=
e
,
μ
), and right-handed
W
R
bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS ...experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8
TeV
corresponding to an integrated luminosity of 19.7
fb
-
1
. For models with strict left-right symmetry, and assuming only one
N
ℓ
flavor contributes significantly to the
W
R
decay width, the region in the two-dimensional
(
M
W
R
,
M
N
ℓ
)
mass plane excluded at a 95 % confidence level extends to approximately
M
W
R
=
3.0
TeV
and covers a large range of neutrino masses below the
W
R
boson mass, depending on the value of
M
W
R
. This search significantly extends the
(
M
W
R
,
M
N
ℓ
)
exclusion region beyond previous results.
A search for the exotic meson X(5568) decaying into the B_{s}^{0}π^{±} final state is performed using data corresponding to 9.6 fb^{-1} from ppover ¯ collisions at sqrts=1960 GeV recorded by the ...Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of B_{s}^{0} produced through the X(5568)→B_{s}^{0}π^{±} process.
A measurement of the W boson pair production cross section in proton-proton collisions at
s
=
8
TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated ...luminosity of 19.4
fb
-1
. The
W
+
W
-
candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured
W
+
W
-
cross section is
60.1
±
0.9
(stat)
±
3.2
(exp)
±
3.1
(theo)
±
1.6
(lumi)
\,pb
=
60.1
±
4.8
\,pb
, consistent with the standard model prediction. The
W
+
W
-
cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are
-
5.7
<
c
WWW
/
Λ
2
<
5.9
TeV
-
2
,
-
11.4
<
c
W
/
Λ
2
<
5.4
TeV
-
2
,
-
29.2
<
c
B
/
Λ
2
<
23.9
TeV
-
2
, in the HISZ basis.
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