4,702 research outputs found
Hadron detection with a dual-readout fiber calorimeter
In this paper, we describe measurements of the response functions of a
fiber-based dual- readout calorimeter for pions, protons and multiparticle
"jets" with energies in the range from 10 to 180 GeV. The calorimeter uses lead
as absorber material and has a total mass of 1350 kg. It is complemented by
leakage counters made of scintillating plastic, with a total mass of 500 kg.
The effects of these leakage counters on the calorimeter performance are
studied as well. In a separate section, we investigate and compare different
methods to measure the energy resolution of a calorimeter. Using only the
signals provided by the calorimeter, we demonstrate that our dual-readout
calorimeter, calibrated with electrons, is able to reconstruct the energy of
proton and pion beam particles to within a few percent at all energies. The
fractional widths of the signal distributions for these particles (sigma/E)
scale with the beam energy as 30%/sqrt(E), without any additional contributing
terms
Dual-Readout Calorimetry with Lead Tungstate Crystals
Results are presented of beam tests in which a small electromagnetic
calorimeter consisting of lead tungstate crystals was exposed to 50 GeV
electrons and pions. This calorimeter was backed up by the DREAM Dual-Readout
calorimeter, which measures the scintillation and \v{C}erenkov light produced
in the shower development, using two different media. The signals from the
crystal calorimeter were analyzed in great detail in an attempt to determine
the contributions from these two types of light to the signals, event by event.
This information makes it possible to eliminate the dominating source of
fluctuations and thus achieve an important improvement in hadronic calorimeter
performance.Comment: Preprint submitted to Nucl. Instrum. Meth. on July 23, 200
Impact of saturation on spin effects in proton-proton scattering
For pomerons described by a sum of two simple-pole terms, a soft and a hard
pomeron, the unitarity bounds from saturation in impact-parameter space are
examined. We consider the effect of these bounds on observables linked with
polarisation, such as the analyzing power in elastic proton-proton scattering,
for LHC energies. We obtain the s and t dependence of the Coulomb-nuclear
interference at small momentum transfer, and show that the effect of the hard
pomeron may be observed at the LHC.Comment: 8 pages, 2 figures, presented by O.V.S. at the Advanced Studies
Institute "Symetries and Spin" (SPIN-Praha-2004), Prague, July 5 - July 10,
200
CMS search plans and sensitivity to new physics with dijets
CMS will use dijets to search for physics beyond the standard model during
early LHC running. The inclusive jet cross section as a function of jet
transverse momentum, with 10 inverse picobarns of integrated luminosity, is
sensitive to contact interactions beyond the reach of the Tevatron. The dijet
mass distribution will be used to search for dijet resonances coming from new
particles, for example an excited quark. Additional sensitivity to the
existence of contact interactions or dijet resonances can be obtained by
comparing dijet rates in two distinct pseudorapidity regions.Comment: 10 pages, 4 figures, accepted for publication in J. Phys. G: Nucl.
Part. Phy
Study of the electron trigger efficiency of the CMS Experiment using test beam data
A study of the electron identification and selection efficiency of the L1
Trigger algorithm has been performed using the combined ECAL/HCAL test beam
data. A detailed discussion of the electron isolation and its impact on the
selection efficiency is presented. The L1 electron algorithm is studied for
different beam energies and the results indicate that efficiencies of 98% or
more can be achieved for electrons with energies between 15 and 100 GeV. The
fraction of charged hadrons with energies from 3 up to 100 GeV rejected by the
L1 electron trigger algorithm is estimated to be larger than 93%.Comment: 22 pages, 14 figure
Dual-readout Calorimetry
The RD52 Project at CERN is a pure instrumentation experiment whose goal is
to understand the fundamental limitations to hadronic energy resolution, and
other aspects of energy measurement, in high energy calorimeters. We have found
that dual-readout calorimetry provides heretofore unprecedented information
event-by-event for energy resolution, linearity of response, ease and
robustness of calibration, fidelity of data, and particle identification,
including energy lost to binding energy in nuclear break-up. We believe that
hadronic energy resolutions of {\sigma}/E 1 - 2% are within reach for
dual-readout calorimeters, enabling for the first time comparable measurement
preci- sions on electrons, photons, muons, and quarks (jets). We briefly
describe our current progress and near-term future plans. Complete information
on all aspects of our work is available at the RD52 website
http://highenergy.phys.ttu.edu/dream/.Comment: 10 pages, 10 figures, Snowmass White pape
Black Holes at Future Colliders and Beyond: a Topical Review
One of the most dramatic consequences of low-scale (~1 TeV) quantum gravity
in models with large or warped extra dimension(s) is copious production of mini
black holes at future colliders and in ultra-high-energy cosmic ray collisions.
Hawking radiation of these black holes is expected to be constrained mainly to
our three-dimensional world and results in rich phenomenology. In this topical
review we discuss the current status of astrophysical observations of black
holes and selected aspects of mini black hole phenomenology, such as production
at colliders and in cosmic rays, black hole decay properties, Hawking radiation
as a sensitive probe of the dimensionality of extra space, as well as an
exciting possibility of finding new physics in the decays of black holes.Comment: 31 pages, 10 figures To appear in the Journal of Physics
The spin dependence of high energy proton scattering
Motivated by the need for an absolute polarimeter to determine the beam
polarization for the forthcoming RHIC spin program, we study the spin
dependence of the proton-proton elastic scattering amplitudes at high energy
and small momentum transfer.We examine experimental evidence for the existence
of an asymptotic part of the helicity-flip amplitude phi_5 which is not
negligible relative to the largely imaginary average non-flip amplitude phi_+.
We discuss theoretical estimates of r_5, essentially the ratio of phi_5 to
phi_+, based upon extrapolation of low and medium energy Regge phenomenological
results to high energies, models based on a hybrid of perturbative QCD and
non-relativistic quark models, and models based on eikonalization techniques.
We also apply the model-independent methods of analyticity and unitarity.The
preponderence of evidence at available energy indicates that r_5 is small,
probably less than 10%. The best available experimental limit comes from
Fermilab E704:those data indicate that |r_5|<15%. These bounds are important
because rigorous methods allow much larger values. In contradiction to a
widely-held prejudice that r_5 decreases with energy, general principles allow
it to grow as fast as ln(s) asymptotically, and some models show an even faster
growth in the RHIC range. One needs a more precise measurement of r_5 or to
bound it to be smaller than 5% in order to use the classical Coulomb-nuclear
interference technique for RHIC polarimetry. As part of this study, we
demonstrate the surprising result that proton-proton elastic scattering is
self-analysing, in the sense that all the helicity amplitudes can, in
principle, be determined experimentally at small momentum transfer without a
knowledge of the magnitude of the beam and target polarization
First experience of using two-dimensional speckle-tracking echocardiography to assess the association of left atrial strain with atrial fibrillation after coronary artery bypass grafting
Aim. To assess left atrial (LA) strain parameters in candidates for coronary artery bypass grafting (CABG) and to evaluate their possible relationship with newly diagnosed atrial fibrillation (AF) after isolated CABG.Material and methods. The study Included 70 patients without prior AF (mean age, 65±8 years; men, 80%). Preoperative speckle-tracking echocardiography with an assessment of LA strain was performed. Two following groups were considered: without postoperative AF (POAF) (n=50), with postoperative POAF (n=20). After surgery, daily electrocardiography (ECG), 3-day postoperative continuous ECG monitoring, Holter ECG monitoring on the 4th-5th day after CABG. The median follow-up was 9 (7; 11) days.Results. Postoperative AF developed in 20/70 (29%) patients. Clinical, demographic and intraoperative parameters of CABG in the groups without and with POAF were comparable. Echocardiographic parameters in the studied groups were also equivalent; LA volume (57,0±8,7 vs 60,0±12,1, respectively), LA size (3,9±0,3 vs 3,9±0,2, respectively). Strain analysis showed its significant decrease in the group with POAF compared to the group without POAF: peak atrial longitudinal strain (PALS) (20,4±3,1 vs 27,8±3,0, respectively), ALS early (8,50±1,5 vs 11,8±1,7, respectively), ALS late (-0,2±0,7 vs -1,0±1,0). ROC analysis established the predictive value of PALS as follows: a value of â€23,0% with a sensitivity of 90% and a specificity of 78% was a predictor of postoperative AF.Conclusion. Conventional echocardiographic predictors (LA size and volume) indicating a high risk of POAF cannot correctly assess the risk of newly diagnosed postoperative arrhythmia. AF after CABG is probably associated with the existing subclinical LA dysfunction as a result of structural abnormalities due to coronary artery disease. Our study showed that a decrease in LA strain parameters is associated with POAF. Further studies are needed to evaluate the contribution of speckle-tracking echocardiography to prediction of POAF
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