594 research outputs found
Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
We perform a global chi^2-analysis of nuclear parton distribution functions
using data from charged current neutrino-nucleus deep-inelastic scattering
(DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that
the nuclear corrections in nu-A DIS are not compatible with the predictions
derived from l^+A DIS and DY data. We quantify this result using a
hypothesis-testing criterion based on the chi^2 distribution which we apply to
the total chi^2 as well as to the chi^2 of the individual data sets. We find
that it is not possible to accommodate the data from nu-A and l^+A DIS by an
acceptable combined fit. Our result has strong implications for the extraction
of both nuclear and proton parton distribution functions using combined
neutrino and charged-lepton data sets.Comment: 5 page
CTEQ Parton Distributions and Flavor Dependence of Sea Quarks
This paper describes salient features of new sets of parton distributions
obtained by the CTEQ Collaboration based on a comprehensive QCD global analysis
of all available data. The accuracy of the new data on deep inelastic
scattering structure functions obtained by the very high statistics NMC and
CCFR experiments provides unprecedented sensitivity to the flavor dependence of
the sea-quark distributions. In addition to much better determination of the
small x dependence of all parton distributions, we found: (i) the strange quark
distribution is much softer than the non-strange sea quarks and rises above the
latter at small-x; and (ii) the difference changes sign as a
function of x. A few alternative sets of viable distributions with conventional
assumptions are also discussed.Comment: 13 pages with figures, MSUHEP-92-27, Fermilab-Pub-92/371,
FSU-HEP-92-1225, ISU-NP-92-1
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
We present the new nCTEQ15 set of nuclear parton distribution functions with
uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear
dependence using data on nuclei all the way up to 208^Pb. The uncertainties are
determined using the Hessian method with an optimal rescaling of the
eigenvectors to accurately represent the uncertainties for the chosen tolerance
criteria. In addition to the Deep Inelastic Scattering (DIS) and Drell-Yan (DY)
processes, we also include inclusive pion production data from RHIC to help
constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of
the data sets with specific nPDF flavor components, and asses the impact of
individual experiments. We also provide comparisons of the nCTEQ15 set with
recent fits from other groups.Comment: 35 page
Widely tunable, non-degenerate three-wave mixing microwave device operating near the quantum limit
We present the first experimental realization of a widely frequency tunable,
non-degenerate three-wave mixing device for quantum signals at GHz frequency.
It is based on a new superconducting building-block consisting of a ring of
four Josephson junctions shunted by a cross of four linear inductances. The
phase configuration of the ring remains unique over a wide range of magnetic
fluxes threading the loop. It is thus possible to vary the inductance of the
ring with flux while retaining a strong, dissipation-free, and noiseless
non-linearity. The device has been operated in amplifier mode and its noise
performance has been evaluated by using the noise spectrum emitted by a voltage
biased tunnel junction at finite frequency as a test signal. The unprecedented
accuracy with which the crossover between zero-point-fluctuations and shot
noise has been measured provides an upper-bound for the noise and dissipation
intrinsic to the device.Comment: Accepted for Physical Review Letters. Supplementary material can be
found in the source packag
Anomalous prompt photon production in hadronic collisions at low-
We investigate the discrepancy that exists at low- between
the next--to--leading order QCD calculations of prompt photon production and
the measured cross section. The central values of the measured cross section
are of order 100\% larger than QCD predictions in this region. It has been
suggested that the bremsstrahlung contribution may account for this
discrepancy. The quark fragmentation function has not been
measured and an exactly known asymptotic form is normally used in calculations.
We examine the effect of much larger fragmentation functions on the QCD
predictions. After illustrating the effect of the large fragmentation functions
in some detail for recent CDF data at =1.8~TeV, we perform a
fit to 8 prompt photon data sets ranging in CMS energy from 24~GeV to 1.8~TeV.
While a large fragmentation function normalization may prove to play an
important role in resolving the discrepancy, the present theoretical and
experimental uncertainties prevent any definite normalization value from being
determined.Comment: 14 pages, LBL-33122 and UCB-PTH-92/38. 13 figures available by email,
specify postscript or topdrawe
Large-x Parton Distributions
Reliable knowledge of parton distributions at large x is crucial for many
searches for new physics signals in the next generation of collider
experiments. Although these are generally well determined in the small and
medium x range, it has been shown that their uncertainty grows rapidly for
x>0.1. We examine the status of the gluon and quark distributions in light of
new questions that have been raised in the past two years about "large-x"
parton distributions, as well as recent measurements which have improved the
parton uncertainties. Finally, we provide a status report of the data used in
the global analysis, and note some of the open issues where future experiments,
including those planned for Jefferson Labs, might contribute.Comment: LaTeX, 9 pages, 7 figures. Invited talk presented at the ``Workshop
on Nucleon Structure in the High x-Bjorken Region (HiX2000),'' Temple
University, Philadelphia, Pennsylvania, March 30-April 1, 200
Compatibility of global NPDF analyses of neutrino DIS and charged-lepton DIS data
The neutrino deep inelastic scattering (DIS) data is very interesting for
global analyses of proton and nuclear parton distribution functions (PDFs)
since they provide crucial information on the strange quark distribution in the
proton and allow for a better flavor decompositon of the PDFs. In order to use
neutrino DIS data in a global analysis of proton PDFs nuclear effects need to
be understood. We study these effects with the help of nuclear PDFs extracted
from global analyses of charged-lepton DIS, Drell-Yan and neutrino DIS data at
next-to-leading order in QCD.Comment: Contribution to the XXIst International Europhysics Conference on
High Energy Physics, 21-27 July 2011, Grenoble, Franc
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