3,555 research outputs found
Challenges for precision measurements at the LHC
Challenges for precision measurements at the LHC are discussed and a proposal
how to move forward to overcome the LHC-specific precision brick-walls is
presented.Comment: 4 pages, Presented at the ICISE Inaugural Conference "Windows on the
Universe" - Quy Nhon, Vietnam, August 11-17, 201
Summary of the Experimental part of the XXXIVth Rencontre de Moriond
I summarise the experimental results presented during the hadronic session of
the XXXIVth Rencontre de Moriond.Comment: Moriond summary talk, Les Arcs, March 20-27, 1999, 15 page
Charge asymmetries of lepton transverse momenta in Drell-Yan processes at the LHC
Charged lepton transverse momenta in the Drell-Yan processes play an
important role at the LHC in precision measurements of the Standard Model
parameters, such as the W-boson mass and width, their charge asymmetries and
sin^2(theta_W). Therefore, their distributions should be described as accurate
as possible by the Monte Carlo event generators. In this paper we discuss the
problem of matching the hard-process kinematics of the Monte Carlo generator
WINHAC with the parton-shower kinematics of the PYTHIA 6.4 generator while
interfacing these two programs. We show that improper assignment of the quark
and antiquark effective momenta in the LO matrix element computations may
affect considerably the predicted lepton transverse momenta and even completely
reverse their charge asymmetries at the LHC. We propose two matching schemes in
which the NLO QCD distributions of the leptonic kinematical variables can be
well reproduced by the LO WINHAC generator.Comment: 18 pages, 8 figure
Drell-Yan processes with WINHAC
We present the Monte Carlo event generator WINHAC for Drell-Yan processes in
proton-proton, proton-antiproton, proton-ion and ion-ion collisions. It
features multiphoton radiation within the Yennie-Frautschi-Suura exclusive
exponentiation scheme with O(alpha) electroweak corrections for the
charged-current (W+/W-) processes and multiphoton radiation generated by PHOTOS
for neutral-current (Z+gamma) ones. For the initial-state QCD/QED parton shower
and hadronisation it is interfaced with PYTHIA. It includes several options,
e.g. for the polarized W-boson production, generation of weighted/unweighted
events, etc. WINHAC was cross-checked numerically at the per-mille level with
independent Monte Carlo programs, such as HORACE and SANC. It has been used as
a basic tool for developing and testing some new methods of precise
measurements of the Standard Model parameters at the LHC, in particular the
W-boson mass. Recently, it has been applied to simulations of double Drell-Yan
processes resulting from double-parton scattering, in order to assess their
influence on the Higgs-boson detection at the LHC in its ZZ and W+W- decay
channels.Comment: 8 pages; presented at the XXXVII International Conference of
Theoretical Physics "Matter To The Deepest", Ustron, Poland, 1-6 September
2013; to appear in Acta Physica Polonica
Luminosity measurement method for the LHC: The detector requirements studies
Absolute normalisation of the LHC measurements with a precision of O(1%) is
desirable but beyond the reach of the present LHC detectors. This series of
papers proposes and evaluates a measurement method capable to achieve such a
precision target. In our earlier paper we have selected the phase-space region
where the lepton pair production cross section in pp collisions at the LHC can
be controlled with < 1 % precision and is large enough to reach a comparable
statistical accuracy of the absolute luminosity measurement on the day-by-day
basis. In the present one the performance requirements for a dedicated
detector, indispensable to efficiently select events in the proposed
phase-space region, are discussed.Comment: 26 pages, 13 figure
Morphological predictors of sleep apnoea severity
Background: Obstructive sleep apnoea (OSA) does not always depend on obesity but on a certain morphological configuration. The study objective was to verify a hypothesis about a relation between anthropometric features and OSA occurrence and severity.
Materials and methods: The study involved 138 patients, who had reported in Department and Clinic of Otolaryngology, Warsaw Medical University, due to suspected OSA. Each patient underwent morphological evaluation according to visual analogue scales. The assessment involved nasal septum morphology evaluation according to a 4-grade scale, palate morphology evaluation according to the 4-grade Friedman scale, whereas the facial profile, oropharyngeal isthmus, and the shape of the nasopharynx were assessed according to our own 3-grade scale.
Results: Statistical analysis confirmed the high concordance of the basic polysomnographic parameters with the Friedman scale and the shape of the oropharyngeal isthmus.
Conclusions: 1. The modified Mallampati score as well as evaluation of the shape of the oropharyngeal isthmus demonstrated high concordance with the basic polysomnographic parameters. 2. The neck circumference is a significant predictor of the apnoea-hypopnoea index value in males suffering from the OSA syndrom
Location of the narrowest area of the pharynx regarding body mass index and obstructive sleep apnoea severity
Background: Among authors studying morphological determinants of the obstructive sleep apnoea (OSA) controversies exist on the location of the narrowest area within the pharynx, critical for development of obstruction. Those disagreements primarily revolve around differences between obese and nonobese OSA patients. Determination whether the location and size of the narrowest area within the pharynx differentiates the obese and nonobese OSA patients.
Materials and methods: A population of 55 subjects was investigated after being diagnosed with OSA in the Polysomnography Laboratory of the Department and Clinic of Otolaryngology in the Medical University of Warsaw, Poland. Additionally a head computed tomography (CT) was performed in all the subjects. The CT images were used to do several crucial measurements which described the geometry of the facial skeleton as well as soft tissues of the head. The obtained results were correlated with apnoea-hypopnoea index (AHI) and body mass index (BMI) values. The data were statistically analysed.
Results: The distance between the hard palate and posterior pharyngeal wall parallel to the horizontal plane as well as the shortest distance between the soft palate and posterior pharyngeal wall significantly differentiated patients in the subgroups by AHI but not by BMI.
Conclusions: Pharyngeal obstruction at the level of the hard and soft palate differentiates patients with severe OSA from patients with mild and moderate OSA regardless of BMI
Luminosity Measurement Method for LHC: The theoretical precision and the experimental challenges
This is the first of the series of papers which present a precision method of the day-by-day monitoring of the absolute LHC luminosity. The method is based on the measurement of the rate of coplanar lepton pairs produced in peripheral collisions of the beams' particles. In the present paper we evaluate the modeling precision of the lepton pair production processes in proton-proton collisions, optimize the measurement region to achieve better than 1% accuracy of the predicted rates, and discuss the experimental challenges to filter out the luminosity monitoring lepton pairs at LHC
Gamma Factory high-intensity muon and positron source -- exploratory studies
One of the fundamental challenges for the future leptonic colliders and
neutrino factories as well as for the high-sensitivity studies of lepton
universality is to design and construct new high-intensity sources of muons and
positrons. The next-generation sources should increase the intensity of the
presently operating ones by at least three orders of the magnitude and include
an important option of producing longitudinally polarised leptons. The main
effort to achieve this goal has been focused, so far, on the proton-beam-driven
muon sources and electron-beam-driven positron sources. In this paper, we
present exploratory studies of an alternative scheme which is based on
high-intensity megawatt-class photon beams. Such beams could be delivered in
the future by the Gamma Factory (GF) project. One of the GF multiple goals is
to increase the energy range (by more than one order of magnitude) and the
intensity (by more than six orders of magnitude) of the presently operating
photon sources. Such a leap can be achieved by extending the present
hadron-collider modus operandi of the LHC with the new GF-operation-mode,
allowing to collide atomic beams with laser pulses. The exploratory studies
presented in this paper demonstrate that more than 10 muons of both
signs and more than 10 electrons/positrons per second can be produced by
the GF source
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