1,419 research outputs found
Measurement of Neutrino-Electron Scattering Cross-Section with a CsI(Tl) Scintillating Crystal Array at the Kuo-Sheng Nuclear Power Reactor
The elastic scattering cross-section was measured with
a CsI(Tl) scintillating crystal array having a total mass of 187kg. The
detector was exposed to an average reactor flux of
at the Kuo-Sheng Nuclear Power
Station. The experimental design, conceptual merits, detector hardware, data
analysis and background understanding of the experiment are presented. Using
29882/7369 kg-days of Reactor ON/OFF data, the Standard Model(SM) electroweak
interaction was probed at the squared 4-momentum transfer range of . The ratio of experimental to SM cross-sections
of was measured. Constraints on
the electroweak parameters were placed, corresponding to a weak
mixing angle measurement of \s2tw = 0.251 \pm 0.031({\it stat}) \pm
0.024({\it sys}) . Destructive interference in the SM \nuebar -e process was
verified. Bounds on anomalous neutrino electromagnetic properties were placed:
neutrino magnetic moment at \mu_{\nuebar}< 2.2 \times 10^{-10} \mu_{\rm B}
and the neutrino charge radius at -2.1 \times 10^{-32} ~{\rm cm^{2}} <
\nuchrad < 3.3 \times 10^{-32} ~{\rm cm^{2}}, both at 90% confidence level.Comment: 18 Figures, 7 Tables; published version as V2 with minor revision
from V
Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets
The HARP collaboration has presented measurements of the double-differential
pi+/pi- production cross-section in the range of momentum 100 MeV/c <= p 800
MeV/c and angle 0.35 rad <= theta <= 2.15 rad with proton beams hitting thin
nuclear targets. In many applications the extrapolation to long targets is
necessary. In this paper the analysis of data taken with long (one interaction
length) solid cylindrical targets made of carbon, tantalum and lead is
presented. The data were taken with the large acceptance HARP detector in the
T9 beam line of the CERN PS. The secondary pions were produced by beams of
protons with momenta 5 GeV/c, 8 GeV/c and 12 GeV/c. The tracking and
identification of the produced particles were performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident protons were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential yields per target nucleon d2
sigma / dp dtheta. The measurements are compared with predictions of the MARS
and GEANT4 Monte Carlo simulations.Comment: 43 pages, 20 figure
Absolute Momentum Calibration of the HARP TPC
In the HARP experiment the large-angle spectrometer is using a cylindrical
TPC as main tracking and particle identification detector. The momentum scale
of reconstructed tracks in the TPC is the most important systematic error for
the majority of kinematic bins used for the HARP measurements of the
double-differential production cross-section of charged pions in proton
interactions on nuclear targets at large angle. The HARP TPC operated with a
number of hardware shortfalls and operational mistakes. Thus it was important
to control and characterize its momentum calibration. While it was not possible
to enter a direct particle beam into the sensitive volume of the TPC to
calibrate the detector, a set of physical processes and detector properties
were exploited to achieve a precise calibration of the apparatus. In the
following we recall the main issues concerning the momentum measurement in the
HARP TPC, and describe the cross-checks made to validate the momentum scale. As
a conclusion, this analysis demonstrates that the measurement of momentum is
correct within the published precision of 3%.Comment: To be published by JINS
Large-angle production of charged pions by 3 GeV/c - 12 GeV/c protons on carbon, copper and tin targets
A measurement of the double-differential production cross-section
in proton--carbon, proton--copper and proton--tin collisions in the range of
pion momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad \le \theta
<2.15 \rad is presented. The data were taken with the HARP detector in the T9
beam line of the CERN PS. The pions were produced by proton beams in a momentum
range from 3 \GeVc to 12 \GeVc hitting a target with a thickness of 5% of a
nuclear interaction length. The tracking and identification of the produced
particles was done using a small-radius cylindrical time projection chamber
(TPC) placed in a solenoidal magnet. An elaborate system of detectors in the
beam line ensured the identification of the incident particles. Results are
shown for the double-differential cross-sections at four incident proton beam
momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc)
Measurement of the CKM angle γ from a combination of B±→Dh± analyses
A combination of three LHCb measurements of the CKM angle γ is presented. The decays B±→D K± and
B±→Dπ± are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+K−, π+π−, K±π∓, K±π∓π±π∓, K0Sπ+π−, or K0S K+K− final states. All measurements use a dataset corresponding to 1.0 fb−1 of integrated luminosity. Combining results from B±→D K± decays alone a best-fit value of
γ =72.0◦ is found, and confidence intervals are set
γ ∈ [56.4,86.7]◦ at 68% CL,
γ ∈ [42.6,99.6]◦ at 95% CL.
The best-fit value of γ found from a combination of results from B±→Dπ± decays alone, is γ =18.9◦,
and the confidence intervals
γ ∈ [7.4,99.2]◦ ∪ [167.9,176.4]◦ at 68% CL
are set, without constraint at 95% CL. The combination of results from B± → D K± and B± → Dπ±
decays gives a best-fit value of γ =72.6◦ and the confidence intervals
γ ∈ [55.4,82.3]◦ at 68% CL,
γ ∈ [40.2,92.7]◦ at 95% CL
are set. All values are expressed modulo 180◦, and are obtained taking into account the effect of D0–D0
mixing
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Measurement of the production cross-section of positive pions in the collision of 8.9 GeV/c protons on beryllium
The double-differential production cross-section of positive pions,
, measured in the HARP experiment is presented.
The incident particles are 8.9 GeV/c protons directed onto a beryllium target
with a nominal thickness of 5% of a nuclear interaction length. The measured
cross-section has a direct impact on the prediction of neutrino fluxes for the
MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons
on target produced about 96,000 reconstructed secondary tracks which were used
in this analysis. Cross-section results are presented in the kinematic range
0.75 GeV/c < < 6.5 GeV/c and 30 mrad < < 210 mrad in
the laboratory frame.Comment: 39 pages, 21 figures. Version accepted for publication by Eur. Phys.
J.
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