The first study of W boson production in pPb collisions is presented, for bosons decaying to a muon or electron, and a neutrino. The measurements are based on a data sample corresponding to an ...integrated luminosity of 34.6 nb−1 at a nucleon–nucleon centre-of-mass energy of sNN=5.02 TeV, collected by the CMS experiment. The W boson differential cross sections, lepton charge asymmetry, and forward–backward asymmetries are measured for leptons of transverse momentum exceeding 25 GeV/c, and as a function of the lepton pseudorapidity in the |ηlab|<2.4 range. Deviations from the expectations based on currently available parton distribution functions are observed, showing the need for including W boson data in nuclear parton distribution global fits.
Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4 fb−1 of ...integrated luminosity from proton–proton collisions at a center-of-mass energy of 8 TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385 GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350 GeV at 95% confidence level. Previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835 GeV.
We report an indirect search for nonstandard model physics using the flavor-changing neutral current decays B→K(*)μ(+)μ(-). We reconstruct the decays and measure their angular distributions, as a ...function of q(2)=M(μμ)(2)c(2), where M(μμ) is the dimuon mass, in pp¯ collisions at √s=1.96 TeV using a data sample corresponding to an integrated luminosity of 6.8 fb(-1). The transverse polarization asymmetry A(T)(2) and the time-reversal-odd charge-and-parity asymmetry A(im) are measured for the first time, together with the K* longitudinal polarization fraction F(L) and the muon forward-backward asymmetry A(FB) for the decays B(0)→K(*0)μ(+)μ(-) and B(+)→K(*+)μ(+)μ(-). The B→K*μ(+)μ(-) forward-backward asymmetry in the most sensitive kinematic regime, 1≤q(2)<6 GeV(2)/c(2), is measured to be A(FB)=0.29(-0.23)(+0.20)(stat)±0.07(syst), the most precise result to date. No deviations from the standard model predictions are observed.
A
bstract
Production of prompt J/
ψ
meson pairs in proton-proton collisions at
s
= 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of ...about 4.7 fb
−1
. The two J/
ψ
mesons are fully reconstructed via their decays into
μ
+
μ
−
pairs. This observation provides for the first time access to the high-transverse-momentum region of J/
ψ
pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/
ψ
transverse momentum (
p
T
J/
ψ
) and rapidity (|
y
J/
ψ
|): |
y
J/
ψ
| < 1.2 for
p
T
J/
ψ
> 6.5 GeV/
c
; 1.2 < |
y
J/
ψ
| < 1.43 for a
p
T
threshold that scales linearly with |
y
J/
ψ
| from 6.5 to 4.5 GeV/
c
; and 1.43 < |
y
J/
ψ
| < 2.2 for
p
T
J/
ψ
> 4.5 GeV/
c
. The total cross section, assuming unpolarized prompt J/
ψ
pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/
ψ
polarization imply modifications to the cross section ranging from −31% to +27%.
A search for new physics in proton-proton collisions having final states with an electron or muon and missing transverse energy is presented. The analysis uses data collected in 2012 with the CMS ...detector, at an LHC center-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of 19.7 fb super(-1). No significant deviation of the transverse mass distribution of the charged lepton-neutrino system from the standard model prediction is found. Mass exclusion limits of up to 3.28 TeV at 95% confidence level for a W'-boson with the same couplings as that of the standard model W-boson are determined. Results are also derived in the framework of split universal extra dimensions, and exclusion limits on Kaluza-Klein (ProQuest: Formulae and/or non-USASCII text omitted) states are found. The final state with large missing transverse energy also enables a search for dark matter production with a recoiling W-boson, with limits set on the mass and the production cross section of potential candidates. Finally, limits are established for a model including interference between a left-handed W'-boson and the standard model W-boson and for a compositeness model.
We report the observation of single top-quark production using 3.2 fb(-1) of ppover collision data with sqrts=1.96 TeV collected by the Collider Detector at Fermilab. The significance of the ...observed data is 5.0 standard deviations, and the expected sensitivity for standard model production and decay is in excess of 5.9 standard deviations. Assuming m(t) = 175 GeV/c(2), we measure a cross section of 2.3(-0.5);(+0.6)(stat + syst) pb, extract the CKM matrix-element value |V(tb)| = 0.91 + or - 0.11(stat + syst) + or - 0.07(theory), and set the limit |V(tb)| > 0.71 at the 95% C.L.
A
bstract
Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of ...19.5 fb
−1
, collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from
t
t
¯
W
or
t
t
¯
Z
decays. The
t
t
¯
W
cross section is measured to be 382
− 102
+ 117
fb with a significance of 4.8 standard deviations from the background-only hypothesis. The
t
t
¯
Z
cross section is measured to be 242
− 55
+ 65
fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the
t
t
¯
W
and
t
t
¯
Z
cross sections.
Higgs boson studies at the Tevatron 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 combine searches by the CDF and DO Collaborations for the standard model Higgs boson with mass in the range 90- 200 GeV /c super(2) produced in the gluon-gluon fusion, WH, ZH, ttH, and vector ...boson fusion processes, and decaying in the H arrow right bb, H arrow right W super(+)W super(-), H arrow right ZZ, H arrow right tau super(+)tau super(-), and H arrow right gamma gamma modes. The data correspond to integrated luminosities of up to 10 fb super(-1) and were collected at the Fermilab Tevatron in pp collisions at radicals = 1.96 TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV /c super(2). The local significance corresponds to 3.0 standard deviations at mH = 125 GeV /c super(2), consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for H arrow right bb, H arrow right W super(+)W super(-), H arrow right tau super(+)t super(-), and H arrow right gamma gamma . The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV /c super(2).
A
bstract
The decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at ...the LHC at
s
=
7
TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Δϕ, between the Mueller-Navelet jets, the average cosines of (
π
− Δ
ϕ
), 2(
π
− Δ
ϕ
), and 3(
π
− Δ
ϕ
), and ratios of these cosines. The jets are required to have transverse momenta,
p
T
, in excess of 35 GeV and rapidities, |
y
|, of less than 4.7. The results are presented as a function of the rapidity separation, Δ
y
, between the Mueller-Navelet jets, reaching Δ
y
up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes.
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