arXiv subjects

A. Kozlov

Publications and source records attributed to A. Kozlov.

47 records · Page 3Linked to original sources

arXiv2011

Design, Construction, Operation and Performance of a Hadron Blind Detector for the PHENIX Experiment

A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure CF4. It has a 50 cm long radiator directly coupled in a window- less configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.

physics.ins-det↗

arXiv2005

A Hadron Blind Detector for the PHENIX Experiment at RHIC

A Hadron Blind Detector (HBD) is being developed for the PHENIX experiment at RHIC. It consists of a Cherenkov radiator operated with pure CF4 directly coupled in a windowless configuration to a triple-GEM detector element with a CsI photocathode and pad readout. The HBD operates in the bandwidth 6-11.5 eV(110-200 nm). We studied the detector response to minimum ionizing particles and to electrons. We present measurements of the CsI quantum efficiency, which are in very good agreement with previously published results over the bandwidth 6-8.3 eV and extend them up to 10.3 eV. Discharge probability andaging studies of the GEMs and the CsI photocathode in pure CF4 are presented.

physics.ins-det↗

arXiv2004

A Measurement of the Exclusive 3He(e,e'p) Reaction Below the Quasi-Elastic Peak

New, high-precision measurements of the 3He(e,e'p) reaction using the A1 collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasi-elastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on Plane Wave Impulse Approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross section, but significant differences remain.

nucl-ex↗

arXiv2003

Development of a triple GEM UV-photon detector operated in pure CF4 for the PHENIX experiment

Results obtained with a triple GEM detector operated in pure CF4 with and without a reflective CsI photocathode are presented. The detector operates in a stable mode at gains up to 10^4. A deviation from exponential growth starts to develop when the total charge exceeds ~ 4 10^6 e leading to gain saturation when the total charge is ~ 2 10^7 e and making the structure relatively robust against discharges. No aging effects are observed in the GEM foils after a total accumulated charge of ~ 10 mC/cm^2 at the anode. The ion back-flow current to the reflective photocathode is comparable to the electron current to the anode. However, no significant degradation of the CsI photocathode is observed for a total ion back-flow charge of ~ 7 mC/cm^2.

physics.ins-det↗

arXiv2003

Proposal for a Hadron Blind Detector for PHENIX

A Hadron Blind Detector (HBD) is proposed as upgrade of the PHENIX detector at RHIC, BNL. The HBD will allow the measurement of low-mass e+e- pairs from the decay of the light vector mesons rho, omega, phi and the low-mass continuum in Au-Au collisions at energies up to sqrt{s_{NN}}= 200 GeV. From MC simulations and general considerations, the HBD has to identify electrons with very high efficiency (> 90%), double hit recognition better than 90%, moderate pion rejection factor of ~200 and radiation budget of the order of 1% of a radiation length. The first choice under study is a windowless Cherenkov detector, operated with pure CF4, in a special proximity focus configuration with a CsI photocathode and a multistage GEM amplification element.

physics.ins-det↗

arXiv2002

Evidence for High-Momentum Enhancement in the Exclusive 3He(e,e'p) Reaction Below the Quasi-Elastic Peak

New, high-precision measurements of the 3He(e,e'p) reaction using the A1 collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in parallel kinematics at energy transfers below the quasi-elastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable enhancements of the cross sections for missing momenta larger than 100 MeV/c as compared to Plane Wave Impulse Approximation were observed in both the two- and three-body breakup channels.

nucl-ex↗

arXiv2002

New empirical fits to the proton electromagnetic form factors

Recent measurements of the ratio of the elastic electromagnetic form factors of the proton, G_Ep/G_Mp, using the polarization transfer technique at Jefferson Lab show that this ratio decreases dramatically with increasing Q^2, in contradiction to previous measurements using the Rosenbluth separation technique. Using this new high quality data as a constraint, we have reanalyzed most of the world e-p elastic cross section data. In this paper, we present a new empirical fit to the reanalyzed data for the proton elastic magnetic form factor in the region 0 < Q^2 < 30 GeV^2. As well, we present an empirical fit to the proton electromagnetic form factor ratio, G_Ep/G_Mp, which is valid in the region 0.1 < Q^2 < 6 GeV^2.

hep-ex↗

arXiv2001

Measurement of GEp/GMp in ep -> ep to Q2 = 5.6 GeV2

The ratio of the electric and magnetic form factors of the proton, GEp/GMp, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic $\vec ep \to e\vec p$ reaction. The new data presented in this article span the range 3.5 < Q2 < 5.6 GeV2 and are well described by a linear Q2 fit. Also, the ratio QF2p/F1p reaches a constant value above Q2=2 GeV2.

nucl-ex↗

arXiv2000

Polarization transfer in the $^{4}$He$(\vec{e},e' \vec{p}^{3}$H reaction

Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.

nucl-ex↗

arXiv2000

The focal plane proton-polarimeter for the 3-spectrometer setup at MAMI

For experiments of the type A(\vec e,e'\vec p) the 3-spectrometer setup of the A1 collaboration at MAMI has been supplemented by a focal plane proton-polarimeter. To this end, a carbon analyzer of variable thickness and two double-planes of horizontal drift chambers have been added to the standard detector system of Spectrometer A. Due to the spin precession in the spectrometer magnets, all three polarization components at the target can be measured simultaneously. The performance of the polarimeter has been studied using elastic p(e,e'p) scattering.

nucl-ex↗

arXiv1999

The Longitudinal and Transverse Response of the 4He(e,e'p) Reaction in the Dip Region

A high-resolution study of the (e,e'p) reaction on Helium-4 was carried out at the Institut fuer Kernphysik in Mainz, Germany. The measurements were done in parallel kinematics (momentum transfer q=685 MeV/c, energy transfer omega=334 MeV) at different incident beam energies in order to enable the Rosenbluth separation of the longitudinal and transverse response functions.

nucl-ex↗