4 research outputs found
New parton distributions in fixed flavour factorization scheme from recent deep-inelastic-scattering data
We present our QCD analysis of the proton structure function
to determine the parton distributions at the next-to-leading order (NLO). The
heavy quark contributions to , with = , have been
included in the framework of the `fixed flavour number scheme' (FFNS). The
results obtained in the FFNS are compared with available results such as the
general-mass variable-flavour-number scheme (GM-VFNS) and other prescriptions
used in global fits of PDFs. In the present QCD analysis, we use a wide range
of the inclusive neutral-current deep-inelastic-scattering (NC DIS) data,
including the most recent data for charm , bottom , longitudinal
structure functions and also the reduced DIS cross sections
from HERA experiments. The most recent HERMES data for
proton and deuteron structure functions are also added. We take into account
ZEUS neutral current DIS inclusive jet cross section data from HERA
together with the recent Tevatron Run-II inclusive jet cross section data from
CDF and D{\O}. The impact of these recent DIS data on the PDFs extracted from
the global fits are studied. We present two families of PDFs, {\tt KKT12} and
{\tt KKT12C}, without and with HERA `combined' data sets on DIS. We
find these are in good agreement with the available theoretical models.Comment: 23 pages, 26 figures and 4 tables. V3: Only few comments and
references added in the replaced version, results unchanged. Code can be
found at http://particles.ipm.ir/links/QCD.ht
Precise charm-quark mass from deep-inelastic scattering.
We present a determination of the charm-quark mass in the MSbar scheme using
the data combination of charm production cross section measurements in
deep-inelastic scattering at HERA. The framework of global analyses of the
proton structure accounts for all correlations of the charm-quark mass with the
other non-perturbative parameters, most importantly the gluon distribution
function in the proton and the strong coupling constant alpha_s(M_Z). We obtain
at next-to-leading order in QCD the value m_c(m_c) = 1.15 +- 0.04 (exp)
+0.04/-0.00 (scale) GeV and at approximate next-to-next-to-leading order
m_c(m_c) = 1.24 +- 0.03 (exp) +0.03/-0.02 (scale) +0.00/-0.07 (theory) GeV with
an accuracy competitive with other methods.Comment: 10 pages latex, 3 figure
Determination of the charm-quark mass in the MS-bar scheme using charm production data from deep inelastic scattering at HERA
We determine the charm-quark mass mc(mc) in the MS-bar scheme using
measurements of charm production in deep-inelastic ep scattering at HERA in the
kinematic range of photon virtuality from 5 to 1000 GeV squared and Bjorken
scaling variable from 0.0001 to 0.5. The extraction of charm quark mass from
this process with space-like kinematics provides complementary information to
results from hadronic processes. The QCD analysis of the HERA data yields a
value of mc(mc) of 1.27 plus minus 0.05(exp) plus 0.06 minus 0.01(scale) GeV at
next-to-leading order and mc(mc) of 1.36 plus minus 0.04(exp) plus 0.04 minus
0.00 (scale) plus minus 0.1(theory) GeV at approximate next-to-next-to-leading
order. The results are consistent with and of comparable precision as the world
average