211 research outputs found
The T2K ND280 Off-Axis Pi-Zero Detector
The Pi-Zero detector (P{\O}D) is one of the subdetectors that makes up the
off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino
experiment. The primary goal for the P{\O}D is to measure the relevant cross
sections for neutrino interactions that generate pi-zero's, especially the
cross section for neutral current pi-zero interactions, which are one of the
dominant sources of background to the electron neutrino appearance signal in
T2K. The P{\O}D is composed of layers of plastic scintillator alternating with
water bags and brass sheets or lead sheets and is one of the first detectors to
use Multi-Pixel Photon Counters (MPPCs) on a large scale.Comment: 17 pages, submitted to NIM
Parity-Violating Electron Scattering from 4He and the Strange Electric Form Factor of the Nucleon
We have measured the parity-violating electroweak asymmetry in the elastic
scattering of polarized electrons from ^4He at an average scattering angle
= 5.7 degrees and a four-momentum transfer Q^2 = 0.091 GeV^2. From
these data, for the first time, the strange electric form factor of the nucleon
G^s_E can be isolated. The measured asymmetry of A_PV = (6.72 +/- 0.84 (stat)
+/- 0.21 (syst) parts per million yields a value of G^s_E = -0.038 +/- 0.042
(stat) +/- 0.010 (syst), consistent with zero
Precision Measurement of the Neutron Spin Asymmetries and Spin-dependent Structure Functions in the Valence Quark Region
We report on measurements of the neutron spin asymmetries and
polarized structure functions at three kinematics in the deep
inelastic region, with , 0.47 and 0.60 and , 3.5 and 4.8
(GeV/c), respectively. These measurements were performed using a 5.7 GeV
longitudinally-polarized electron beam and a polarized He target. The
results for and at are consistent with previous world
data and, at the two higher points, have improved the precision of the
world data by about an order of magnitude. The new data show a zero
crossing around and the value at is significantly positive.
These results agree with a next-to-leading order QCD analysis of previous world
data. The trend of data at high agrees with constituent quark model
predictions but disagrees with that from leading-order perturbative QCD (pQCD)
assuming hadron helicity conservation. Results for and have a
precision comparable to the best world data in this kinematic region. Combined
with previous world data, the moment was evaluated and the new result
has improved the precision of this quantity by about a factor of two. When
combined with the world proton data, polarized quark distribution functions
were extracted from the new values based on the quark parton
model. While results for agree well with predictions from various
models, results for disagree with the leading-order pQCD
prediction when hadron helicity conservation is imposed.Comment: A typing error in A_\parallel(3He) at x=0.47 in Table VII of Phys.
Rev. C has been noticed and correcte
Precision Measurement of the Neutron Spin Asymmetry and Spin-Flavor Decomposition in the Valence Quark Region
We have measured the neutron spin asymmetry with high precision at
three kinematics in the deep inelastic region at , 0.47 and 0.60, and
, 3.5 and 4.8 (GeV/c), respectively. Our results unambiguously
show, for the first time, that crosses zero around and becomes
significantly positive at . Combined with the world proton data,
polarized quark distributions were extracted. Our results, in general, agree
with relativistic constituent quark models and with perturbative quantum
chromodynamics (pQCD) analyses based on the earlier data. However they deviate
from pQCD predictions based on hadron helicity conservation.Comment: 5 pages, 2 figures, this is the final version appeared in Phys. Rev.
Let
Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2
We report the most precise measurement to date of a parity-violating
asymmetry in elastic electron-proton scattering. The measurement was carried
out with a beam energy of 3.03 GeV and a scattering angle =6
degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per
million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor
combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/-
0.012 (FF) where the first two errors are experimental and the last error is
due to the uncertainty in the neutron electromagnetic form factor. This result
significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2.
A consistent picture emerges when several measurements at about the same Q^2
value are combined: G_E^s is consistent with zero while G_M^s prefers positive
values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one
figure to improve focu
Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches
The LUX-ZEPLIN (LZ) experiment will search for dark matter particle
interactions with a detector containing a total of 10 tonnes of liquid xenon
within a double-vessel cryostat. The large mass and proximity of the cryostat
to the active detector volume demand the use of material with extremely low
intrinsic radioactivity. We report on the radioassay campaign conducted to
identify suitable metals, the determination of factors limiting radiopure
production, and the selection of titanium for construction of the LZ cryostat
and other detector components. This titanium has been measured with activities
of U~1.6~mBq/kg, U~0.09~mBq/kg,
Th~~mBq/kg, Th~~mBq/kg, K~0.54~mBq/kg, and Co~0.02~mBq/kg (68\% CL).
Such low intrinsic activities, which are some of the lowest ever reported for
titanium, enable its use for future dark matter and other rare event searches.
Monte Carlo simulations have been performed to assess the expected background
contribution from the LZ cryostat with this radioactivity. In 1,000 days of
WIMP search exposure of a 5.6-tonne fiducial mass, the cryostat will contribute
only a mean background of (stat)(sys) counts.Comment: 13 pages, 3 figures, accepted for publication in Astroparticle
Physic
Search for short baseline nu(e) disappearance with the T2K near detector
8 pages, 6 figures, submitted to PRD rapid communication8 pages, 6 figures, submitted to PRD rapid communicationWe thank the J-PARC staff for superb accelerator performance and the CERN NA61 collaboration for providing valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC and CFI, Canada; Commissariat `a l’Energie Atomique and Centre National de la Recherche Scientifique–Institut National de Physique Nucle´aire et de Physique des Particules, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; Russian Science Foundation, RFBR and Ministry of Education and Science, Russia; MINECO and European Regional Development Fund, Spain; Swiss National Science Foundation and State Secretariat for Education, Research and Innovation, Switzerland; STFC, UK; and DOE, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK. In addition participation of individual researchers and institutions has been further supported by funds from ERC (FP7), EU; JSPS, Japan; Royal Society, UK; DOE Early Career program, USA
Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 x 10(20) protons on target
111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee commentsWe thank the J-PARC staff for superb accelerator performance and the CERN NA61/SHINE Collaboration for providing valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC, and CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR and MES, Russia; MINECO and ERDF funds, Spain; SNSF and SER, Switzerland; STFC, UK; and the U. S. Deparment of Energy, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK, and the Emerald High Performance Computing facility in the Centre for Innovation, UK. In addition, participation of individual researchers and institutions has been further supported by funds from ERC (FP7), EU; JSPS, Japan; Royal Society, UK; and DOE Early Career program, USA
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