96 research outputs found
SUSY-QCD corrections to stop annihilation into electroweak final states including Coulomb enhancement effects
We present the full supersymmetric QCD corrections
for stop-anti-stop annihilation into electroweak final states within the
Minimal Supersymmetric Standard Model (MSSM). We also incorporate Coulomb
corrections due to gluon exchange between the incoming stops. Numerical results
for the annihilation cross sections and the predicted neutralino relic density
are presented. We show that the impact of the radiative corrections on the
cosmologically preferred region of the parameter space can become larger than
the current experimental uncertainty, shifting the relic bands within the
considered regions of the parameter space by up to a few tens of GeV.Comment: 20 pages, 13 figures, updated to version published in Phys. Rev.
Strange Quark PDFs and Implications for Drell-Yan Boson Production at the LHC
Global analyses of Parton Distribution Functions (PDFs) have provided
incisive constraints on the up and down quark components of the proton, but
constraining the other flavor degrees of freedom is more challenging.
Higher-order theory predictions and new data sets have contributed to recent
improvements. Despite these efforts, the strange quark PDF has a sizable
uncertainty, particularly in the small x region. We examine the constraints
from experiment and theory, and investigate the impact of this uncertainty on
LHC observables. In particular, we study W/Z production to see how the s-quark
uncertainty propagates to these observables, and examine the extent to which
precise measurements at the LHC can provide additional information on the
proton flavor structure.Comment: 14 pages, 11 figures, added reference
Full O(alpha) corrections to e+e- -> sf_i sf_j
We present a complete precision analysis of the sfermion pair production
process e+e- -> sf_i sf_j (f = t, b, tau, nu_tau) in the Minimal Supersymmetric
Standard Model. Our results extend the previously calculated weak corrections
by including all one-loop corrections together with higher order QED
corrections. We present the details of the analytical calculation and discuss
the renormalization scheme. The numerical analysis shows the results for total
cross-sections, forward-backward and left-right asymmetries. It is based on the
SPS1a' point from the SPA project. The complete corrections are about 10% and
have to be taken into account in a high precision analysis.Comment: 32 pages, 24 figures, RevTeX
Spectral estimates for two-dimensional Schroedinger operators with application to quantum layers
A logarithmic type Lieb-Thirring inequality for two-dimensional Schroedinger
operators is established. The result is applied to prove spectral estimates on
trapped modes in quantum layers
Revision of the \u3cem\u3eMesobuthus caucasicus\u3c/em\u3e complex from Central Asia, with descriptions of six new species (Scorpiones: Buthidae)
A widespread Mesobuthus caucasicus complex, which includes some of the most common scorpions found from the Caucasus to China, is revised for the first time based on new extensive collections from Central Asia, using both morphological and DNA marker data. Mesobuthus caucasicus (Nordmann, 1840), s.str. is restricted to the Caucasus Mts. Four taxa are elevated to species rank: M. fuscus (Birula, 1897) (Tajikistan), M. intermedius (Birula, 1897) (Tajikistan), M. kaznakovi (Birula, 1904) (Tajikistan, Uzbekistan), and M. parthorum (Pocock, 1889) (Afghanistan, Iran, Turkmenistan). Six new species are described: M. brutus sp. n. (Iran), M. elenae sp. n. (Tajikistan, Uzbekistan), M. gorelovi sp. n. (Kazakhstan, Turkmenistan, Uzbekistan), M. kreuzbergi sp. n. (Tajikistan, Uzbekistan), M. mischi sp. n. (Afghanistan), and M. nenilini sp. n. (Uzbekistan). The most common species in Central Asia is a psammophilic Mesobuthus gorelovi sp. n., widespread through lowland sand deserts across Turkmenistan (Karakum), Uzbekistan (Kizylkum), and Kazakhstan (north to Baigakum and Moyinkum). A key to all studied species is provided. A DNA phylogeny based on COI and 16S rRNA markers is presented including nine Central Asian species (M. elenae sp. n., M. fuscus, M. gorelovi sp. n., M. intermedius, M. kaznakovi, M. kreuzbergi sp. n., M. mischi sp. n., M. nenilini sp. n., and M. parthorum) and M. caucasicus from Turkey. A deep phylogenetic diversity across Central Asia is revealed. Historical biogeographic scenarios for this scorpion group are discussed, including fragmentation in mountain valleys and expansion across sand deserts in Central Asia. The monotypic scorpion genus Afghanobuthus Lourenço, 2005 and its single species A. naumanni Lourenço, 2005, from Afghanistan, are demonstrated to be junior synonyms, respectively, of Mesobuthus Vachon, 1950, and M. parthorum (Pocock, 1889) from the same area
Impact of heavy quark and quarkonium data on nuclear gluon PDFs
A clear understanding of nuclear parton distribution functions (nPDFs) plays
a crucial role in the interpretation of collider data taken at the Relativistic
Heavy Ion Collider (RHIC), the Large Hadron Collider (LHC) and in the near
future at the Electron-Ion Collider (EIC). Even with the recent inclusions of
vector boson and light meson production data, the uncertainty of the gluon PDF
remains substantial and limits the interpretation of heavy ion collision data.
To obtain new constraints on the nuclear gluon PDF, we extend our recent
nCTEQ15WZ+SIH analysis to inclusive quarkonium and open heavy-flavor meson
production data from the LHC. This vast new data set covers a wide kinematic
range and puts strong constraints on the nuclear gluon PDF down to . The theoretical predictions for these data sets are obtained from a
data-driven approach, where proton-proton data are used to determine effective
scattering matrix elements. This approach is validated with detailed
comparisons to existing next-to-leading order (NLO) calculations in
non-relativistic QCD (NRQCD) for quarkonia and in the general-mass
variable-flavor-number scheme (GMVFNS) for the open heavy-flavored mesons. In
addition, the uncertainties from the data-driven approach are determined using
the Hessian method and accounted for in the PDF fits. This extension of our
previous analyses represents an important step toward the next generation of
PDFs not only by including new data sets, but also by exploring new methods for
future analyses
Impact of LHC vector boson production in heavy ion collisions on strange PDFs
The extraction of the strange quark parton distribution function (PDF) poses a long-standing puzzle. Measurements from neutrino-nucleus deep inelastic scattering (DIS) experiments suggest the strange quark is suppressed compared to the light sea quarks, while recent studies of W^\pm /Z boson production at the LHC imply a larger strange component at small x values. As the parton flavor determination in the proton depends on nuclear corrections, e.g. from heavy-target DIS, LHC heavy ion measurements can provide a distinct perspective to help clarify this situation. In this investigation we extend the nCTEQ nPDFs to study the impact of the LHC proton-lead W^\pm /Z production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC W^\pm /Z proton analyses and the neutrino-nucleus DIS data. We identify these new nPDFs as nCTEQWZ. Our calculations are performed using a new implementation of the nCTEQ code (nCTEQ++) based on C++ which enables us to easily interface to external programs such as HOPPET, APPLgrid and MCFM. Our results indicate that, as suggested by the proton data, the small x nuclear strange sea appears larger than previously expected, even when the normalization of the W^{\pm }/Z data is accommodated in the fit. Extending the nCTEQ analysis to include LHC W^\pm /Z data represents an important step as we advance toward the next generation of nPDFs
Impact of LHC vector boson production in heavy ion collisions on strange PDFs
The extraction of the strange quark parton distribution function (PDF) poses a long-standing puzzle. Measurements from neutrino-nucleus deep inelastic scattering (DIS) experiments suggest the strange quark is suppressed compared to the light sea quarks, while recent studies of W^\pm /Z boson production at the LHC imply a larger strange component at small x values. As the parton flavor determination in the proton depends on nuclear corrections, e.g. from heavy-target DIS, LHC heavy ion measurements can provide a distinct perspective to help clarify this situation. In this investigation we extend the nCTEQ nPDFs to study the impact of the LHC proton-lead W^\pm /Z production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC W^\pm /Z proton analyses and the neutrino-nucleus DIS data. We identify these new nPDFs as nCTEQWZ. Our calculations are performed using a new implementation of the nCTEQ code (nCTEQ++) based on C++ which enables us to easily interface to external programs such as HOPPET, APPLgrid and MCFM. Our results indicate that, as suggested by the proton data, the small x nuclear strange sea appears larger than previously expected, even when the normalization of the W^{\pm }/Z data is accommodated in the fit. Extending the nCTEQ analysis to include LHC W^\pm /Z data represents an important step as we advance toward the next generation of nPDFs
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