The CLAS forward electromagnetic calorimeter

Precise determination of the deuteron spin structure at low to moderate Q^{2} with CLAS and extraction of the neutron contribution We present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron ( 15 ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry A d 1 and the polarized structure function g d 1 were extracted over a wide kinematic range (0.05 GeV 2 < Q 2 < 5 GeV 2 and 0.9 GeV < W < 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions A n 1 and g n 1 of the (bound) neutron, which are so far unknown in the resonance region, W < 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.

Section: The Experimentsmentioning

confidence: 99%

Precise determination of the deuteron spin structure at low to moderateQ2with CLAS and extraction of the neutron contribution

Guler¹,

Fersch²,

Kuhn³

et al. 2015

“…The gaps between the cryostats are instrumented with six identical detector packages. Each sector consists of drift chambers (DC) [41] for charged particle tracking, Cherenkov counters (CC) [42] for electron identification, scintillator counters (SC) [43] for charged particle identification, and electromagnetic calorimeters (EC) [44] for electron identification and detection of neutral particles. A 5-cm-long liquid-hydrogen target was located 25 cm upstream of the nominal center of CLAS.…”

Section: Experiments Description and Data Analysismentioning

confidence: 99%

Separated structure functions for exclusiveK+ΛandK+Σ0electroproduction at 5.5 GeV measured with CLAS

Carman¹,

Park²,

Raue³

et al. 2013

Self Cite

We report measurements of the exclusive electroproduction of K + Λ and K + Σ 0 final states from an unpolarized proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions σ U , σ LT , σ T T , and σ LT ′ were extracted from the Φ-dependent differential cross sections acquired with a longitudinally polarized 5.499 GeV electron beam. The data span a broad range of momentum transfers Q 2 from 1.4 to 3.9 GeV 2 , invariant energy W from threshold to 2.6 GeV, and nearly the full center-of-mass angular range of the kaon. The separated structure functions provide an unprecedented data sample, which in conjunction with other meson photo-and electroproduction data, will help to constrain the higher-level analyses being performed to search for missing baryon resonances.

“…The regions between the cryostats are instrumented with six identical detector packages, also referred to as "sectors". Each sector consists of four Start Counter (ST) paddles [33] mainly used for triggering purposes, three regions of Drift Chambers (R1, R2, and R3) [34] to determine the trajectories of the charged particles,Čerenkov Counters (CC) [35] for electron identification, Scintillator Counters (SC) [36] for charged particle identification based on the Time-OfFlight (TOF) method, and Electromagnetic Calorimeters (EC) [37] used for electron identification and detection of neutral particles.…”

Section: Apparatusmentioning

confidence: 99%

Upper limits for the photoproduction cross section for theΦ−−(1860)pentaquark state off the deuteron

Egiyan¹,

Langheinrich²,

Gothe³

et al. 2012

Self Cite

We searched for the Φ −− (1860) pentaquark in the photoproduction process off the deuteron in the Ξ − π − decay channel using CLAS. The invariant mass spectrum of the Ξ − π − system does not indicate any statistically significant enhancement near the reported mass M = 1.860 GeV. The statistical analysis of the sideband-subtracted mass spectrum yields a 90% confidence level upper limit of 0.7 nb for the photoproduction cross section of Φ −− (1860) with a consecutive decay into Ξ − π − in the photon energy range 4.5 GeV < Eγ < 5.5 GeV.