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 π0\pi^0, η\eta and η′\eta' in the Coulomb field of a nucleus

Photoproduction of neutral pseudoscalar mesons $\pi^0,\eta(547)$ and $\eta'(958)$ 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 $C$-parity odd Regge trajectories. In the coherent production the isospin filtering makes the $\omega(782)$ a dominant trajectory. The calculations are in agreement with $\pi^0$ 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 $\eta$ and $\eta'$ 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

A New Measurement of the π0\pi^0 Radiative Decay Width

High precision measurements of the differential cross sections for $\pi^0$ photoproduction at forward angles for two nuclei, $^{12}$C and $^{208}$Pb, have been performed for incident photon energies of 4.9 - 5.5 GeV to extract the ${\pi^0 \to \gamma\gamma}$ decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The ${\pi^0 \to \gamma\gamma}$ 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 $\Gamma{(\pi^0 \to \gamma\gamma)} = 7.82 \pm 0.14 ~({\rm stat.}) \pm 0.17 ~({\rm syst.}) ~{\rm eV}$. 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

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 $\pi^0\rightarrow\gamma\gamma$ decay amplitude. Based on this anomaly and its small ($\simeq$ 4.5%) chiral correction, a firm prediction of the $\pi^0$ lifetime can be used as a test of QCD at confinement scale energies. The interesting experimental and theoretical histories of the $\pi^0$ meson are reviewed, from discovery to the present era. Experimental results are in agreement with the theoretical prediction, within the current ($\simeq$ 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 $\simeq$ 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