4,532 research outputs found
Nucleon PDF separation with the collider and fixed-target data
We consider the impact of the recent data obtained by the LHC, Tevatron, and fixed-target experiments on the nucleon
quark distributions with a particular focus on disentangling different quark species. An improved determination
of the poorly known strange sea distribution is obtained due to including data from the neutrino-induced deep-inelastic
scattering experiments NOMAD and CHORUS. The impact of the associated (W + c) production data by CMS and
ATLAS on the strange sea determination is also studied and a comparison with earlier results based on the collider
data is discussed. Finally, the recent LHC and Tevatron data on the charged lepton asymmetry are compared to the
NNLO ABM predictions and the potential of this input in improving the non-strange sea distributions is evaluate
Prediction of charm-production fractions in neutrino interactions
The way a charm-quark fragments into a charmed hadron is a challenging
problem both for the theoretical and the experimental particle physics.
Moreover, in neutrino induced charm-production, peculiar processes occur such
as quasi-elastic and diffractive charm-production which make the results from
other experiments not directly comparable. We present here a method to extract
the charmed fractions in neutrino induced events by using results from
, , experiments while taking into account the
peculiarities of charm-production in neutrino interactions. As results, we
predict the fragmentation functions as a function of the neutrino energy and
the semi-muonic branching ratio, , and compare them with the available
data
Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction
A Neutrino Factory producing an intense beam composed of nu_e(nubar_e) and
nubar_mu(nu_mu) from muon decays has been shown to have the greatest
sensitivity to the two currently unmeasured neutrino mixing parameters,
theta_13 and delta_CP . Using the `wrong-sign muon' signal to measure nu_e to
nu_mu(nubar_e to nubar_mu) oscillations in a 50 ktonne Magnetised Iron Neutrino
Detector (MIND) sensitivity to delta_CP could be maintained down to small
values of theta_13. However, the detector efficiencies used in previous studies
were calculated assuming perfect pattern recognition. In this paper, MIND is
re-assessed taking into account, for the first time, a realistic pattern
recognition for the muon candidate. Reoptimisation of the analysis utilises a
combination of methods, including a multivariate analysis similar to the one
used in MINOS, to maintain high efficiency while suppressing backgrounds,
ensuring that the signal selection efficiency and the background levels are
comparable or better than the ones in previous analyses
Physics with charm particles produced in neutrino interactions. A historical recollection
Results obtained in neutrino unteractions on charm particles are presented
Associated Charm Production in Neutrino-Nucleus Interactions
In this paper a search for associated charm production both in neutral and
charged current -nucleus interactions is presented. The improvement of
automatic scanning systems in the {CHORUS} experiment allows an efficient
search to be performed in emulsion for short-lived particles. Hence a search
for rare processes, like the associated charm production, becomes possible
through the observation of the double charm-decay topology with a very low
background. About 130,000 interactions located in the emulsion target
have been analysed. Three events with two charm decays have been observed in
the neutral-current sample with an estimated background of 0.180.05. The
relative rate of the associated charm cross-section in deep inelastic
interactions, has been
measured. One event with two charm decays has been observed in charged-current
interactions with an estimated background of 0.180.06 and the
upper limit on associated charm production in charged-current interactions at
90% C.L. has been found to be .Comment: 10 pages, 4 figure
Polarization phenomena in open charm photoproduction processes
We analyze polarization effects in associative photoproduction of
pseudoscalar () charmed mesons in exclusive processes , , . Circularly polarized photons
induce nonzero polarization of the -hyperon with - and -components
(in the reaction plane) and non vanishing asymmetries and for polarized nucleon target. These polarization observables can be
predicted in model-independent way for exclusive -production processes
in collinear kinematics. The T-even -polarization and asymmetries for
non-collinear kinematics can be calculated in framework of an effective
Lagrangian approach. The depolarization coefficients , characterizing
the dependence of the -polarization on the nucleon polarization are also
calculated.Comment: 36 pages 13 figure
Leading order analysis of neutrino induced dimuon events in the CHORUS experiment
We present a leading order QCD analysis of a sample of neutrino induced
charged-current events with two muons in the final state originating in the
lead-scintillating fibre calorimeter of the CHORUS detector. The results are
based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign
dimuon events collected during the exposure of the detector to the CERN Wide
Band Neutrino Beam between 1995 and 1998. % with GeV
and GeV collected %between 1995 and 1998. The analysis yields a
value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a
value of the ratio of the strange to non-strange sea in the nucleon of , improving the results obtained in similar analyses
by previous experiments.Comment: Submitted to Nuclear Physics
Testing Deconfinement at High Isospin Density
We study the transition from hadronic matter to a mixed phase of quarks and
hadrons at high baryon and isospin densities reached in heavy ion collisions.
We focus our attention on the role played by the nucleon symmetry energy at
high density.In this respect the inclusion of a scalar isovector meson, the
\delta-coupling, in the Hadron Lagrangian appears rather important. We study in
detail the formation of a drop of quark matter in the mixed phase, and we
discuss the effects on the quark drop nucleation probability of the finite size
and finite time duration of the high density region. We find that, if the
parameters of quark models are fixed so that the existence of quark stars is
allowed, then the density at which a mixed phase starts forming drops
dramatically in the range Z/A \sim 0.3--0.4. This opens the possibility to
verify the Witten-Bodmer hypothesis on absolute stability of quark matter using
ground-based experiments in which neutron-rich nuclei are employed. These
experiments can also provide rather stringent constraints on the Equation of
State (EoS) to be used for describing the pre-Supernova gravitational collapse.
Consistent simulations of neutron rich heavy ion collisions are performed in
order to show that even at relatively low energies, in the few AGeV range, the
system can enter such unstable mixed phase. Some precursor observables are
suggested, in particular a ``neutron trapping'' effect.Comment: 32 pages, 14 figures, elsart late
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
Forward production of charged pions with incident on nuclear targets measured at the CERN PS
Measurements of the double-differential production cross-section
in the range of momentum 0.5 \GeVc \leq p \le 8.0 \GeVc and angle 0.025 \rad
\leq \theta \le 0.25 \rad in interactions of charged pions on beryllium,
carbon, aluminium, copper, tin, tantalum and lead are presented. These data
represent the first experimental campaign to systematically measure forward
pion hadroproduction. The data were taken with the large acceptance HARP
detector in the T9 beam line of the CERN PS. Incident particles, impinging on a
5% nuclear interaction length target, were identified by an elaborate system of
beam detectors. The tracking and identification of the produced particles was
performed using the forward spectrometer of the HARP detector. Results are
obtained for the double-differential cross-sections mainly at four incident pion beam
momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). The measurements are compared
with the GEANT4 and MARS Monte Carlo simulationComment: to be published on Nuclear Physics
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