We report measurements of transverse momentum $p_t$ spectra for ten event multiplicity classes of p-p collisions at $\sqrt{s} = 200$ GeV. By analyzing the multiplicity dependence we find that the ...spectrum shape can be decomposed into a part with amplitude proportional to multiplicity and described by a Lévy distribution on transverse mass $m_t$, and a part with amplitude proportional to multiplicity squared and described by a gaussian distribution on transverse rapidity $y_t$. The functional forms of the two parts are nearly independent of event multiplicity. The two parts can be identified with the soft and hard components of a two-component model of p-p collisions. This analysis then provides the first isolation of the hard component of the $p_t$ spectrum as a distribution of simple form on $y_t$.
We present recent results of single-spin asymmetry \(A_N\) measurements in \(\pi^0\) inclusive production. Asymmetry was measured in \(\pi^-p\) and \(pp\) interactions at 40 and 70 GeV ...correspondingly. Significant asymmetry was observed in the polarized target fragmentation region. The results are in agreement with "universal threshold" of single-spin asymmetry.
We present a systematic analysis of two-pion interferometry in Au+Au collisions at \(\sqrt{s_{\rm{NN}}}\) = 62.4 GeV and Cu+Cu collisions at \(\sqrt{s_{\rm{NN}}}\) = 62.4 and 200 GeV using the STAR ...detector at RHIC. The multiplicity and transverse momentum dependences of the extracted correlation lengths (radii) are studied. The scaling with charged particle multiplicity of the apparent system volume at final interaction is studied for the RHIC energy domain. The multiplicity scaling of the measured correlation radii is found to be independent of colliding system and collision energy.
A precise measurement of the angle \(\alpha\) in the CKM triangle is very important for a complete test of Standard Model. A theoretically clean method to extract \(\alpha\) is provided by B\(^0 \to ...\rho \pi\) decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal to background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tree and penguin contributions, was carried out. It was shown that in one year of data taking BTeV could achieve an accuracy on \(\alpha\) better than 5\(^{\circ}\).
Nucl.Instrum.Meth. A510 (2003) 248-261 The energy dependence of the energy and position resolutions of the
electromagnetic calorimeter prototype made of lead tungstate crystals produced
in ...Bogoroditsk (Russia) and Shanghai (China) is presented. These
measurementswere carried out at the Protvino accelerator using a 1 to 45 GeV
electron beam. The crystals were coupled to photomultiplier tubes. The
dependence of energy and position resolutions on different factors as well as
the measured electromagnetic shower lateral profile are presented.
Nucl.Instrum.Meth. A512 (2003) 488-505 We report on the effects of radiation on the light output of lead tungstate
crystals. The crystals were irradiated by pure, intense high energy electron
and ...hadron beams as well as by a mixture of hadrons, neutrons and gammas. The
crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai
(China). These studies were carried out at the 70-GeV proton accelerator in
Protvino.
Nucl.Instrum.Meth. A510 (2003) 211-218 A beam line for electrons with energies in the range of 1 to 45 GeV, low
contamination of hadrons and muons and high intensity up to 10^6 per
accelerator spill ...at 27 GeV was setup at U70 accelerator in Protvino, Russia. A
beam tagging system based on drift chambers with 160 micron resolution was able
to measure relative electron beam momentum precisely. The resolution sigma_p p
was 0.13% at 45 GeV where multiple scattering is negligible. This test beam
setup provided the possibility to study properties of lead tungstate crystals
(PbWO_4) for the BTeV experiment at Fermilab.
We report on the performance of a monitoring system for a prototype calorimeter for the BTeV experiment that uses Lead Tungstate crystals coupled with photomultiplier tubes. The tests were carried ...out at the 70 GeV accelerator complex at Protvino, Russia.
Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of ...paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystals recovery from such damage.
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