101 research outputs found
The GRAAL high resolution BGO calorimeter and its energy calibration and monitoring system
We describe the electromagnetic calorimeter built for the GRAAL apparatus at
the ESRF. Its monitoring system is presented in detail. Results from tests and
the performance obtained during the first GRAAL experiments are given. The
energy calibration accuracy and stability reached is a small fraction of the
intrinsic detector resolution.Comment: 19 pages, 14 figures, submitted to Nuclear Instruments and Method
Further studies on pyrazolo[1',5':1,6]pyrimido[4,5-d]pyridazin-4(3H)-ones as potent and selective human A1 adenosine receptor antagonists.
A new series of pyrazolo[1',5':1,6]pyrimido[4,5-dlpyridazin-4(3H)-ones was synthesized and tested in radioligand binding assays on human A(1), A(2A) and A(3) adenosine receptors. Most of the compounds showed high selectivity of action towards A(1) receptor and high affinity with K-i values in the low nanomolar range. The pharmacological profile of the most active molecules towards A(1) adenosine receptors was evaluated in cAMP functional assay. Compounds demonstrated their ability to completely counteract the effect of the agonist NECA, thus demonstrating their antagonist profile. Moreover, the most interesting compound, tested in the mouse passive avoidance, exhibited an antiamnesic effect at the doses of 10 and 30 mg/kg. (C) 2014 Published by Elsevier Masson SAS
ep â ep Ïâ° Reaction Studied in the Î(1232) Mass Region Using Polarization Asymmetries
Measurements of the angular distributions of target and double-spin asymmetries for the Î+(1232) in the exclusive channel â p(âe,e\u27p)Ï0 obtained at the Jefferson Lab in the Q2 range from 0.5 to 1.5 GeV2/c2 are presented. Results of the asymmetries are compared with the unitary isobar model [D. Drechsel , Nucl. Phys. A645, 145 (1999)], dynamical models [T. Sato and T. S. Lee, Phys. Rev. C 54, 2660 (1996); S. S. Kamalov , Phys. Lett. B 27, 522 (2001)], and the effective Lagrangian theory [R. M. Davidson , Phys. Rev. D 43, 71 (1991)]. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly
Exclusive Electroproduction of á” Mesons at 4.2 GeV
We studied the exclusive reaction ep â e\u27 p\u27 á” using the á” âK+K- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in Q2 from 0.7 to 2.2 GeV2and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of á” production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time c Î t below 2 fm. At c Î t = 0.6 fm, we measure bÉž = 2.27 ± 0.42 GeV-2. The cross section dependence on W as W0.2 ±0.1 at Q2, 1.3 GeV2 was determined by comparison with Éž production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction
Corrected Article: Exclusive Electroproduction of á” Mesons at 4.2 GeV [Physical. Rev. C 63, 065205, (2001)]
We studied the exclusive reaction ep â e\u27 p\u27 á” using the á” âK+K- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in Q2 from 0.7 to 2.2 GeV2and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of á” production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time c Î t below 2 fm. At c Î t = 0.6 fm, we measure bÉž = 2.27 ± 0.42 GeV-2. The cross section dependence on W as W0.2 ±0.1 at Q2, 1.3 GeV2 was determined by comparison with Éž production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction
Kinematically Complete Measurement of the Proton Structure Function Fâ in the Resonance Region and Evaluation of its Moments
We measured the inclusive electron-proton cross section in the nucleon resonance region (W \u3c2.5 GeV) at momentum transfers Q2 below 4.5 (GeV/c)2 with the CLAS detector. The large acceptance of CLAS allowed the measurement of the cross section in a large, contiguous two-dimensional range of Q2 and x, making it possible to perform an integration of the data at fixed Q2 over the significant x interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q2 evolution of its moments, Mn(Q2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and will require significant improvements in theoretical predictions if a meaningful comparison with these new experimental results is to be made
Measurement of Inclusive Spin Structure Functions of the Deuteron
We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer [Q2 = 0.27-1.3 (GeV/c)2] and final hadronic state mass in the nucleon resonance region (W=1.08-2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target (15ND3) and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry Aâ„ and the spin structure function g1d. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function g1d and study its approach to both the deep inelastic limit at large Q2 and to the Gerasimov-Drell-Hearn sum rule at the real photon limit (Q2â 0). We find that the first moment varies rapidly in the Q2 range of our experiment and crosses zero at Q2 between 0.5 and 0.8 (GeV/c)2, indicating the importance of the Delta resonance at these momentum transfers
Measurement of ep â e \u27 p ÏâșÏâ» and Baryon Resonance Analysis
The cross section for the reaction epâ e\u27pÏ+Ï- was measured in the resonance region for 1.4 2 \u3c 1.5 GeV2/c2using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on N* and Î states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the P13(1720) resonance or by introducing a new baryon state, not reported in published analyses
Measurement of the Polarized Structure Function for in the Resonance Region
The polarized longitudinal-transverse structure function
has been measured using the reaction in the
resonance region at and 0.65 GeV. No previous
data exist for this reaction channel. The kinematically
complete experiment was performed at Jefferson Lab with the CEBAF Large
Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an
energy of 1.515 GeV. A partial wave analysis of the data shows generally better
agreement with recent phenomenological models of pion electroproduction
compared to the previously measured channel. A fit to both
and channels using a unitary isobar model suggests the unitarized
Born terms provide a consistent description of the non-resonant background. The
-channel pion pole term is important in the channel through a
rescattering correction, which could be model-dependent.Comment: 6 pages, LaTex, 5 eps figures: Submitted to PRC/Brief Reports v2:
Updated referenc
Measurement of Inclusive Spin Structure Functions of the Deuteron
We report the results of a new measurement of spin structure functions of the
deuteron in the region of moderate momentum transfer ( = 0.27 -- 1.3
(GeV/c)) and final hadronic state mass in the nucleon resonance region (
= 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam
at Jefferson Lab off a dynamically polarized cryogenic solid state target
(ND) and detected the scattered electrons with the CEBAF Large
Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal
double spin asymmetry and the spin structure function . Our
data are generally in reasonable agreement with existing data from SLAC where
they overlap, and they represent a substantial improvement in statistical
precision. We compare our results with expectations for resonance asymmetries
and extrapolated deep inelastic scaling results. Finally, we evaluate the first
moment of the structure function and study its approach to both the
deep inelastic limit at large and to the Gerasimov-Drell-Hearn sum rule
at the real photon limit (). We find that the first moment varies
rapidly in the range of our experiment and crosses zero at between
0.5 and 0.8 (GeV/c), indicating the importance of the resonance at
these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys.
Rev.
- âŠ