3,096 research outputs found
Searching for intrinsic charm in the proton at the LHC
Despite rather long-term theoretical and experimental studies, the hypothesis
of the non-zero intrinsic (or valence-like) heavy quark component of the proton
distribution functions has not yet been confirmed or rejected. The LHC with
-collisions at 7--14 TeV will obviously supply extra unique
information concerning the above-mentioned component of the proton. To use the
LHC potential, first of all, one should select the parton-level (sub)processes
(and final-state signatures) that are most sensitive to the intrinsic heavy
quark contributions. To this end inclusive production of -jets
accompanied by photons is considered. On the basis of the performed theoretical
study it is demonstrated that the investigation of the intrinsic heavy quark
contributions looks very promising at the LHC in processes such as
.Comment: 13 pages, 6 figure
Measurement of the energy resolution and calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip
This paper describes an iterative method of per-pixel energy calibration of
hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip. A
convolution of precisely measured spectra of characteristic X-rays of different
metals with the resolution and the efficiency of the pixel detector is used for
the calibration. The energy resolution of the detector is also measured during
the calibration. The use of per-pixel calibration allows to achieve a good
energy resolution of the Timepix detector with GaAs:Cr sensor: 8% and 13% at 60
keV and 20 keV, respectively
Alignment and resolution studies of a MARS CT scanner
This paper describes a procedure of alignment of MARS CT scanner with cone beam geometry. The position of the xray source relative to the detector, the tilt of the detector are measured during alignment. The mechanical precision of gantry movement is determined. Significant improvement in the quality of image reconstruction has been achieved as a result of the calibration. Spatial resolution (PTF) of the scanner is confirmed to be about 30 μm
Anomalously interacting new extra vector bosons and their first LHC constraints
In this review phenomenological consequences of the Standard Model extension
by means of new spin-1 chiral fields with the internal quantum numbers of the
electroweak Higgs doublets are summarized. The prospects for resonance
production and detection of the chiral vector and bosons at
the LHC energies are considered. The boson can be observed as a
Breit-Wigner resonance peak in the invariant dilepton mass distributions in the
same way as the well-known extra gauge bosons. However, the bosons
have unique signatures in transverse momentum, angular and pseudorapidity
distributions of the final leptons, which allow one to distinguish them from
other heavy neutral resonances. In 2010, with 40 pb of the LHC
proton-proton data at the energy 7 TeV, the ATLAS detector was used to search
for narrow resonances in the invariant mass spectrum of and
final states and high-mass charged states decaying to a charged
lepton and a neutrino. No statistically significant excess above the Standard
Model expectation was observed. The exclusion mass limits of 1.15 TeV and
1.35 TeV were obtained for the chiral neutral and charged
bosons, respectively. These are the first direct limits on the and
boson production. For almost all currently considered exotic models the
relevant signal is expected in the central dijet rapidity region. On the
contrary, the chiral bosons do not contribute to this region but produce an
excess of dijet events far away from it. For these bosons the appropriate
kinematic restrictions lead to a dip in the centrality ratio distribution over
the dijet invariant mass instead of a bump expected in the most exotic models.Comment: 24 pages, 34 figure, based on talk given by V.A.Bednyakov at 15th
Lomonosov conference, 22.08.201
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
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