302 research outputs found
Precise Measurement of Neutrino and Anti-neutrino Differential Cross Sections on Iron
This thesis will present a precise measurement of the differentialcross section for charged current neutrino and anti-neutrino scatteringfrom iron. The NuTeV experiment took data during 1996-97 and collected and charged-current (CC) interactions. The experiment combines sign-selected neutrino andantineutrino beams and the upgraded CCFR iron-scintillator neutrinodetector. A precision continuous calibration beam was used to determinethe muon and hadron energy scales to a precision of about a factor of two better thanprevious experiments. The structure functions and are extracted and compared with theory and previous measurements
Update of Parton Distributions at NNLO
We present a new set of parton distributions obtained at NNLO. These differ
from the previous sets available at NNLO due to improvements in the theoretical
treatment. In particular we include a full treatment of heavy flavours in the
region near the quark mass. In this way, an essentially complete set of NNLO
partons is presented for the first time. The improved treatment leads to a
significant change in the gluon and heavy quark distributions, and a larger
value of the QCD coupling at NNLO, alpha_S(M_Z^2) = 0.1191 +/- 0.002(expt.) +/-
0.003(theory). Indirectly this also leads to a change in the light partons at
small x and modifications of our predictions for W and Z production at the LHC.
As well as the best-fit set of partons, we also provide 30 additional sets
representing the uncertainties of the partons obtained using the Hessian
approach.Comment: 13 pages, 11 figures. Version published. Slight extension and some
modification of reference
Soft-Gluon Resummation for Heavy Quark Production in Charged-Current Deep Inelastic Scattering
We study soft-gluon radiation for heavy quark production in charged-current
Deep Inelastic Scattering processes. We resum large-x contributions to the
MSbar coefficient function to next-to-leading logarithmic accuracy and present
results for charm quark structure functions for several values of the ratio
m_c/Q. The effect of the resummation turns out to be visible, especially at
small Q^2, and the results exhibit very little dependence on factorization and
renormalization scales. The impact of our calculation on structure function
measurements at NuTeV and HERA experiments is discussed.Comment: 21 pages, 7 figure
Compatibility of neutrino DIS data and global analyses of parton distribution functions
Neutrino\antineutrino deep inelastic scattering (DIS) data provide useful
constrains for the flavor decomposition in global fits of parton distribution
functions (PDF). The smallness of the cross-sections requires the use of
nuclear targets in the experimental setup. Understanding the nuclear
corrections is, for this reason, of utmost importance for a precise
determination of the PDFs. Here, we explore the nuclear effects in the
neutrino\antineutrino-nucleon DIS by comparing the NuTeV, CDHSW, and CHORUS
cross-sections to the predictions derived from the latest parton distribution
functions and their nuclear modifications. We obtain a good description of
these data and find no apparent disagreement between the nuclear effects in
neutrino DIS and those in charged lepton DIS. These results also indicate that
further improvements in the knowledge of the nuclear PDFs could be obtained by
a more extensive use of these sets of neutrino data.Comment: 16 pages, 8 figure
Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions
We study the sensitivity of our recent MSTW 2008 NLO and NNLO PDF analyses to
the values of the charm- and bottom-quark masses, and we provide additional
public PDF sets for a wide range of these heavy-quark masses. We quantify the
impact of varying m_c and m_b on the cross sections for W, Z and Higgs
production at the Tevatron and the LHC. We generate 3- and 4-flavour versions
of the (5-flavour) MSTW 2008 PDFs by evolving the input PDFs and alpha_S
determined from fits in the 5-flavour scheme, including the eigenvector PDF
sets necessary for calculation of PDF uncertainties. As an example of their
use, we study the difference in the Z total cross sections at the Tevatron and
LHC in the 4- and 5-flavour schemes. Significant differences are found,
illustrating the need to resum large logarithms in Q^2/m_b^2 by using the
5-flavour scheme. The 4-flavour scheme is still necessary, however, if cuts are
imposed on associated (massive) b-quarks, as is the case for the experimental
measurement of Z b bbar production and similar processes.Comment: 40 pages, 11 figures. Grids can be found at
http://projects.hepforge.org/mstwpdf/ and in LHAPDF V5.8.4. v2: version
published in EPJ
Nuclear effects in F_3 structure function of nucleon
We study nuclear effects in the structure function in the deep
inelastic neutrino reactions on iron by using a relativistic framework to
describe the nucleon spectral functions in the nucleus.
The results for the ratio and
the Gross-Llewellyn Smith(GLS) integral in
nuclei are discussed and compared with the recent results available in
literature from theoretical and phenomenological analyses of experimental data.Comment: 13 pages, 8 figure
Precision determination of electroweak parameters and the strange content of the proton from neutrino deep-inelastic scattering
We use recent neutrino dimuon production data combined with a global
deep-inelastic parton fit to construct a new parton set, NNPDF1.2, which
includes a determination of the strange and antistrange distributions of the
nucleon. The result is characterized by a faithful estimation of uncertainties
thanks to the use of the NNPDF methodology, and is free of model or theoretical
assumptions other than the use of NLO perturbative QCD and exact sum rules.
Better control of the uncertainties of the strange and antistrange parton
distributions allows us to reassess the determination of electroweak parameters
from the NuTeV dimuon data. We perform a direct determination of the |V_cd| and
|V_cs| CKM matrix elements, obtaining central values in agreement with the
current global CKM fit: specifically we find |V_cd|=0.244\pm 0.019 and
|V_cs|=0.96\pm 0.07. Our result for |V_cs| is more precise than any previous
direct determination. We also reassess the uncertainty on the NuTeV
determination of \sin^2\theta_W through the Paschos-Wolfenstein relation: we
find that the very large uncertainties in the strange valence momentum fraction
are sufficient to bring the NuTeV result into complete agreement with the
results from precision electroweak data.Comment: 46 pages, 20 figures; fig.12 and discussion on positivity added,
several typos corrected. Final version, to be published in Nucl. Phys.
Measurement of Muon Neutrino Quasi-Elastic Scattering on Carbon
The observation of neutrino oscillations is clear evidence for physics beyond
the standard model. To make precise measurements of this phenomenon, neutrino
oscillation experiments, including MiniBooNE, require an accurate description
of neutrino charged current quasi-elastic (CCQE) cross sections to predict
signal samples. Using a high-statistics sample of muon neutrino CCQE events,
MiniBooNE finds that a simple Fermi gas model, with appropriate adjustments,
accurately characterizes the CCQE events observed in a carbon-based detector.
The extracted parameters include an effective axial mass, M_A^eff = 1.23+/-0.20
GeV, that describes the four-momentum dependence of the axial-vector form
factor of the nucleon; and a Pauli-suppression parameter, kappa =
1.019+/-0.011. Such a modified Fermi gas model may also be used by future
accelerator-based experiments measuring neutrino oscillations on nuclear
targets.Comment: 5 pages, 3 figure
Nuclear Shadowing in Electro-Weak Interactions
Shadowing is a quantum phenomenon leading to a non-additivity of electroweak
cross sections on nucleons bound in a nucleus. It occurs due to destructive
interference of amplitudes on different nucleons. Although the current
experimental evidence for shadowing is dominated by charged-lepton nucleus
scattering, studies of neutrino nucleus scattering have recently begun and
revealed unexpected results.Comment: 77 pages, 57 figures. To be published in "Progress in Particle and
Nuclear Physics" 201
First Observation of Coherent Production in Neutrino Nucleus Interactions with 2 GeV
The MiniBooNE experiment at Fermilab has amassed the largest sample to date
of s produced in neutral current (NC) neutrino-nucleus interactions at
low energy. This paper reports a measurement of the momentum distribution of
s produced in mineral oil (CH) and the first observation of coherent
production below 2 GeV. In the forward direction, the yield of events
observed above the expectation for resonant production is attributed primarily
to coherent production off carbon, but may also include a small contribution
from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino
flux, the sum of the NC coherent and diffractive modes is found to be (19.5
1.1 (stat) 2.5 (sys))% of all exclusive NC production at
MiniBooNE. These measurements are of immediate utility because they quantify an
important background to MiniBooNE's search for
oscillations.Comment: Submitted to Phys. Lett.
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