73 research outputs found
Calibration of CMS calorimeters with LHC proton beam deflected by crystal
Calibration of the forward CMS hadron calorimeters in situ by the LHC beam is
proposed. Simulations show that bent crystal channeling technique is feasible
at the LHC, and report the experience of IHEP Protvino in bending 70 GeV
protons by 9 degrees (150 mrad) during 10 years in 1994-2004 experiments.
Practical realization of calibration scheme based on simulations and previous
experience is proposed.Comment: Presented at CARE-HHH-APD Mini-Workshop on Crystal Collimation in
Hadron Storage Rings (CC-2005), Geneva, Switzerland, 7-8 Mar 200
Development of detector active element based on thgem
A thick gas electron multiplier is considered for radiation-hard detectors
(hadron calorimeter). There was carried out technological and design study to
optimize the element structure. The measurements results and the next plans are
presented.Comment: 7 pages, 12 figure
Primakoff production of , and in the Coulomb field of a nucleus
Photoproduction of neutral pseudoscalar mesons and
in the Coulomb field of an atomic nucleus is studied using a model
which describes the Primakoff and nuclear parts of the production amplitude. At
high energies the nuclear background is dominated by the exchange of -parity
odd Regge trajectories. In the coherent production the isospin filtering makes
the a dominant trajectory. The calculations are in agreement with
data from JLAB provided the photon shadowing and final state
interactions of mesons are taken into account. The kinematic conditions which
allow to study the Primakoff effect in and photoproduction off
nuclei are further discussed. We also give predictions for the higher energies
available at the JLAB upgrade.Comment: 15 pages, 14 figures, discussion added, final version to be published
in Phys. Rev.
Forward Yields of the Secondary Light Nuclei in CC-collisions at Beam Energy 20.5 GeV/n on the Accelerator U-70 in Comparison with Models UrQMD, FTFP-BERT-EMV and QGSP-FTFP-BERT-EMV in the Framework of Geant4
The zero angle production of light nuclei has been studied in CC-interactions at beam energy 20.5 GeV/n on accelerator U-70. The measurements were performed with employing of the beamline no. 22 as spectrometer of secondary particles with verying its rigidity from 10 to 70 GeV/c. We observed secondary protons and deuterons with momenta above kinematic limit of NN-interactions. The measured dependence of forward yields on momentum are compared with the model predictions in the framework of Geant4. The models more or less correctly give positions of maxima of the distributions and their general qualitative dependence on the momentum. But in the quantitative predictions of the yields there are significant differences with the experiment which grow with increase of atomic mass number A
Neutral Pion Lifetime Measurements and the QCD Chiral Anomaly
A fundamental property of QCD is the presence of the chiral anomaly, which is
the primary component of the decay amplitude.
Based on this anomaly and its small ( 4.5%) chiral correction, a firm
prediction of the lifetime can be used as a test of QCD at confinement
scale energies. The interesting experimental and theoretical histories of the
meson are reviewed, from discovery to the present era. Experimental
results are in agreement with the theoretical prediction, within the current
( 3%) experimental error; however, they are not yet sufficiently
precise to test the chiral corrected result, which is a firm QCD prediction and
is known to 1% uncertainty. At this level there exist experimental
inconsistencies, which require attention. Possible future work to improve the
present precision is suggested.Comment: 75 pages, 17 figure
A New Measurement of the Radiative Decay Width
High precision measurements of the differential cross sections for
photoproduction at forward angles for two nuclei, C and Pb, have
been performed for incident photon energies of 4.9 - 5.5 GeV to extract the
decay width. The experiment was done at Jefferson
Lab using the Hall B photon tagger and a high-resolution multichannel
calorimeter. The decay width was extracted by
fitting the measured cross sections using recently updated theoretical models
for the process. The resulting value for the decay width is . With the 2.8% total uncertainty, this result is a factor of 2.5 more
precise than the current PDG average of this fundamental quantity and it is
consistent with current theoretical predictions.Comment: 4 pages, 5 figure
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