A
bstract
The energy flow,
dE/dη
, is studied at large pseudorapidities in proton-proton collisions at the LHC, for centre-of-mass energies of 0.9 and 7 TeV. The measurements are made using the CMS ...detector in the pseudorapidity range 3
.
15
<
|
η
|
<
4
.
9, for both minimum-bias events and events with at least two high-momentum jets. The data are compared to various pp Monte Carlo event generators whose theoretical models and input parameter values are sensitive to the energy-flow measurements. Inclusion of multiple-parton interactions in the Monte Carlo event generators is found to improve the description of the energy-flow measurements.
A
bstract
A search for the standard model Higgs boson in the H → ZZ → 2
ℓ
2
ν
decay channel, where
ℓ
= e or
μ
, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were ...collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 fb
−1
. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.
Phys. Rev. C 102, 064905 (2020) The PHENIX experiment at the Relativistic Heavy Ion Collider measured $\pi^0$
and $\eta$ mesons at midrapidity in U$+$U collisions at $\sqrt{s_{_{NN}}}=192$
GeV in a ...wide transverse momentum range. Measurements were performed in the
$\pi^0(\eta)\rightarrow\gamma\gamma$ decay modes. A strong suppression of
$\pi^0$ and $\eta$ meson production at high transverse momentum was observed in
central U$+$U collisions relative to binary scaled $p$$+$$p$ results. Yields of
$\pi^0$ and $\eta$ mesons measured in U$+$U collisions show similar suppression
pattern to the ones measured in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$
GeV for similar numbers of participant nucleons. The $\eta$/$\pi^0$ ratios do
not show dependence on centrality or transverse momentum, and are consistent
with previously measured values in hadron-hadron, hadron-nucleus,
nucleus-nucleus, and $e^+e^-$ collisions.
A measurement of inclusive W and Z production cross sections in pp collisions at
TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector ...at the LHC and corresponding to an integrated luminosity of 36 pb
−1
. The measured inclusive cross sections are
σ
(pp → W
X
) ×
= 10.31 ± 0.02 (stat.) ± 0.09 (syst.) ± 0.10 (th.) ± 0.41 (lumi.) nb and
σ
(pp → Z
X
) ×
= 0.974 ± 0.007 (stat.) ± 0.007 (syst
.
) ± 0.018 (th.) ± 0
.
039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are (
σ
(pp → W
X
) ×
/(
σ
(pp → Z
X
) ×
= 10.54 ± 0.07 (stat.) ± 0.08 (syst.) ± 0.16 (th.) and (
σ
(pp → W
+
X
) ×
/(
σ
(pp → W
−
X
) ×
= 1.421 ± 0.006 (stat.) ± 0.014 (syst.) ± 0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions.
A
bstract
A measurement of the
J/ψ
and
ψ
(2S) production cross sections in pp collisions at
with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of ...37 pb
−1
. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges and integrated in the kinematical regions considered in this study. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B →
ψ
(2S)
X
decay is extracted from the ratio of the non-prompt cross sections to be:
Phys. Rev. Lett. 125, 182001 (2020) We have measured beam-spin asymmetries to extract the $\sin\phi$ moment
$A_{LU}^{\sin\phi}$ from the hard exclusive $\vec{e} p \to e^\prime n \pi^+$
reaction above ...the resonance region, for the first time with nearly full
coverage from forward to backward angles in the center-of-mass. The
$A_{LU}^{\sin\phi}$ moment has been measured up to 6.6 GeV$^{2}$ in $-t$,
covering the kinematic regimes of Generalized Parton Distributions (GPD) and
baryon-to-meson Transition Distribution Amplitudes (TDA) at the same time. The
experimental results in very forward kinematics demonstrate the sensitivity to
chiral-odd and chiral-even GPDs. In very backward kinematics where the TDA
framework is applicable, we found $A_{LU}^{\sin\phi}$ to be negative, while a
sign change was observed near 90$^\circ$ in the center-of-mass. The unique
results presented in this paper will provide critical constraints to establish
reaction mechanisms that can help to further develop the GPD and TDA
frameworks.
A
bstract
The integrated and differential cross sections for the production of pairs of isolated photons is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the CMS ...detector at the LHC. A data sample corresponding to an integrated luminosity of 36 pb
−1
is analysed. A next-to-leading-order perturbative QCD calculation is compared to the measurements. A discrepancy is observed for regions of the phase space where the two photons have an azimuthal angle difference
rad.
The Drell-Yan differential cross section is measured in pp collisions at
TeV, from a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb
−1
. ...The cross section measurement, normalized to the measured cross section in the Z region, is reported for both the dimuon and dielectron channels in the dilepton invariant mass range 15–600 GeV. The normalized cross section values are quoted both in the full phase space and within the detector acceptance. The effect of final state radiation is also identified. The results are found to agree with theoretical predictions.
A
bstract
A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at
TeV, pp → p
μ
+
μ
−
p, is reported using data corresponding to an integrated luminosity of ...40 pb
−1
. For muon pairs with invariant mass greater than 11
.
5 GeV, transverse momentum
p
T
(
μ
)
>
4 GeV and pseudorapidity |
η
(
μ
)|
<
2
.
1, a fit to the dimuon
p
T
(
μ
+
μ
−
) distribution results in a measured cross section of
σ
(p → p
μ
+
μ
−
p) =
(stat
.
) ± 0
.
16 (syst
.
) ± 0
.
14 (lumi
.
) pb, consistent with the theoretical prediction evaluated with the event generator L
pair
. The ratio to the predicted cross section is
(stat
.
) ± 0
.
04 (syst
.
) ± 0
.
03 (lumi
.
). The characteristic distributions of the muon pairs produced via
γγ
fusion, such as the muon acoplanarity, the muon pair invariant mass and transverse momentum agree with those from the theory.
A measurement of the underlying activity in events with a jet of transverse momentum in the several GeV region is performed in proton-proton collisions at
and 7 TeV, using data collected by the CMS ...experiment at the LHC. The production of charged particles with pseudorapidity |
η
| < 2 and transverse momentum
p
T
> 0
.
5 GeV/
c
is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. A significant growth of the average multiplicity and scalar-
p
T
sum of the particles in the transverse region is observed with increasing
p
T
of the leading track-jet, followed by a much slower rise above a few GeV/c. For track-jet
p
T
larger than a few GeV/c, the activity in the transverse region is approximately doubled with a centre-of-mass energy increase from 0
.
9 to 7 TeV. Predictions of several QCD-inspired models as implemented in
pythia
are compared to the data.
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