(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract A search for new physics is performed in multijet events with large missing transverse momentum produced in ...proton-proton collisions at ... = 8 TeV using a data sample corresponding to an integrated luminosity of 19.5 fb^sup -1^ collected with the CMS detector at the LHC. The data sample is divided into three jet multiplicity categories (3-5, 6-7, and greater than or equal to8 jets), and studied further in bins of two variables: the scalar sum of jet transverse momenta and the missing transverse momentum. The observed numbers of events in various categories are consistent with backgrounds expected from standard model processes. Exclusion limits are presented for several simplified supersymmetric models of squark or gluino pair production. Figure not available: see fulltext.
A
bstract
A search for the standard model Higgs boson produced in association with a top-quark pair
t
t
¯
H
is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb
...−1
and 19.7 fb
−1
collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H → hadrons, H → photons, and H → leptons. The results are characterized by an observed
t
t
¯
H
signal strength relative to the standard model cross section,
μ
=
σ/σ
SM
,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is
μ
= 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract Double parton scattering is investigated in proton-proton collisions at ... = 7 TeV where the final state includes ...a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 fb^sup -1^, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W + 2-jet events due to double parton scattering is measured to be 0.055 ± 0.002 (stat.) ± 0.014 (syst.). The effective cross section, sigma ^sub eff^, characterizing the effective transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 ± 0.8(stat.) ± 6.6(syst.)mb. Figure not available: see fulltext.
Abstract A search for new physics is performed based on events with jets and a pair of isolated, same-sign leptons. The results are obtained using a sample of proton-proton collision data collected ...by the CMS experiment at a centre-of-mass energy of 8 TeV at the LHC, corresponding to an integrated luminosity of 19.5 fb^sup -1^. In order to be sensitive to a wide variety of possible signals beyond the standard model, multiple search regions defined by the missing transverse energy, the hadronic energy, the number of jets and b-quark jets, and the transverse momenta of the leptons in the events are considered. No excess above the standard model background expectation is observed and constraints are set on a number of models for new physics, as well as on the same-sign top-quark pair and quadruple-top-quark production cross sections. Information on event selection efficiencies is also provided, so that the results can be used to confront an even broader class of new physics models. Figure not available: see fulltext.
A measurement of the inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton–proton collisions at s=8 TeV are presented. The analysis is based on a data ...sample, corresponding to an integrated luminosity of 19.6 fb−1, collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ→ℓℓℓ′ℓ′, where ℓ=e,μ and ℓ′=e,μ,τ. The measured total cross section σ(pp→ZZ)=7.7±0.5 (stat)−0.4+0.5 (syst)±0.4(theo)±0.2 (lumi) pb, for both Z bosons produced in the mass range 60<mZ<120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings at the 95% confidence level: −0.004<f4Z<0.004, −0.004<f5Z<0.004, −0.005<f4γ<0.005, and −0.005<f5γ<0.005.
A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × ...10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.
A detailed analysis is presented of the diffractive deep-inelastic scattering process ep→eXY, where Y is a proton or a low mass proton excitation carrying a fraction 1-xIP>0.95 of the incident proton ...longitudinal momentum and the squared four-momentum transfer at the proton vertex satisfies |t|<1 GeV2. Using data taken by the H1 experiment, the cross section is measured for photon virtualities in the range 3.5≤Q2≤1600 GeV2, triple differentially in xIP, Q2 and β=x/xIP, where x is the Bjorken scaling variable. At low xIP, the data are consistent with a factorisable xIP dependence, which can be described by the exchange of an effective pomeron trajectory with intercept αIP(0)=1.118±0.008(exp.)+0.029-0.010(model). Diffractive parton distribution functions and their uncertainties are determined from a next-to-leading order DGLAP QCD analysis of the Q2 and β dependences of the cross section. The resulting gluon distribution carries an integrated fraction of around 70% of the exchanged momentum in the Q2 range studied. Total and differential cross sections are also measured for the diffractive charged current process e+p→ν̄eXY and are found to be well described by predictions based on the diffractive parton distributions. The ratio of the diffractive to the inclusive neutral current ep cross sections is studied. Over most of the kinematic range, this ratio shows no significant dependence on Q2 at fixed xIP and x or on x at fixed Q2 and β.
The production of leading neutrons, where the neutron carries a large fraction
x
L
of the incoming proton’s longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The ...data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb
−1
. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6<
Q
2
<100 GeV
2
, Bjorken scaling variable 1.5⋅10
−4
<
x
<3⋅10
−2
, longitudinal momentum fraction 0.32<
x
L
<0.95 and neutron transverse momentum
p
T
<0.2 GeV. The leading neutron structure function,
, and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of
Q
2
,
x
and
x
L
. Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.
In this manuscript, switchable and multi-wavelength erbium-doped fiber laser arrangement, based on Fabry–Perot (FPI) and Mach–Zehnder (MZI) interferometers is presented. Here, the FPI is composed by ...two air-microcavities set into the tip of conventional single mode fiber, this one is used as a partially reflecting mirror and lasing modes generator. And the MZI fabricated by splicing a segment of photonic crystal fiber (PCF) between a single-mode fiber section, was set into an optical fiber loop mirror that acts as full-reflecting and wavelength selective filter. Both interferometers, promotes a cavity oscillation into the fiber laser configuration, besides by curvature applied over the MZI, the fiber laser generates: single, double, triple and quadruple laser emissions with a signal to noise ratio (SNR) of 30dB. These laser emissions can be switching between them from 1525nm to 1534nm by adjusting the curvature radius over the MZI. This laser fiber offers a wavelength and power stability at room temperature, compactness and low implementation cost. Moreover the linear laser proposed can be used in several fields such as spectroscopy, telecommunications and fiber optic sensing systems.
•A switchable and multi-wavelength EDF laser arrangement based on FPI and MZI cavities is analyzed.•The FPI is composed by two air-microcavities.•Single, double, triple and quadruple laser emissions with a SNR of 30dB are presented.•The laser is stable at wavelength and power at room temperature.
Dijet production has been measured in
p
Pb
collisions at a nucleon–nucleon centre-of-mass energy of 5.02
TeV
. A data sample corresponding to an integrated luminosity of 35
nb
-
1
was collected using ...the Compact Muon Solenoid detector at the Large Hadron Collider. The dijet transverse momentum balance, azimuthal angle correlations, and pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters (
E
T
4
<
|
η
|
<
5.2
). For
p
Pb
collisions, the dijet transverse momentum ratio and the width of the distribution of dijet azimuthal angle difference are comparable to the same quantities obtained from a simulated
p
p
reference and insensitive to
E
T
4
<
|
η
|
<
5.2
. In contrast, the mean value of the dijet pseudorapidity is found to change monotonically with increasing
E
T
4
<
|
η
|
<
5.2
, indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The pseudorapidity distribution of the dijet system in minimum bias
p
Pb
collisions is compared with next-to-leading-order perturbative QCD predictions obtained from both nucleon and nuclear parton distribution functions, and the data more closely match the latter.
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