125 research outputs found
Next-to-leading order QCD predictions for graviton and photon associated production in the Large Extra Dimensions model at the LHC
We present the calculations of the complete next-to-leading order(NLO) QCD
corrections to the inclusive total cross sections for the Kaluza-Klein(KK)
graviton and photon associated production process in
the large extra dimensions(LED) model at the LHC. We show that the NLO QCD
corrections in general enhance the total cross sections and reduce the
dependence of the total cross sections on the factorization and renormalization
scales. When jet veto is considered, the NLO corrections reduce the total cross
sections. We also calculate some important differential cross sections for this
process at NLO: the missing transverse momentum distribution, the transverse
momentum distribution and the pseudorapidity distribution of photon.Comment: 28 pages, 14 figures; minor changes, version published in Phys.Rev.
Same-sign top pair production in an extra-dimension model of flavor at the CERN Large Hadron Collider
We study the same-sign top pair production mediated by the first Kluza-Klein
(KK) excitation of the gluon in the Randall-Sundrum (RS) model with flavor
violation at the Large Hadron Collider (LHC), in which the nonuniversal
couplings between fermions and KK gauge bosons will lead to observable tree
level flavor-changing neutral current (FCNC) effects. We find that the
same-sign top quarks produced in our case have property of high energy and high
transverse momentum, and lead to an observable signal in the same-sign dilepton
channel even when the mass of the KK gluon reach up to 3 TeV. We further
investigate the potential of the LHC to probe the flavor violating parameters
and find that the LHC can probe their values down to 0.06.Comment: 12 pages, 4 figures; several references added; version appeared in
Phys.Rev.
Signature of Large Extra Dimensions from Z boson pair production at the CERN Large Hadron Collider
We study the Z boson pair production mediated by the Kaluza-Klein (KK)
graviton in large extra dimensions (LED) at the CERN Large Hadron Collider
(LHC). We use the partial wave unitarity to discuss the constraints on the
process energy scale in order to give a self-consistent calculation. We find
that the LED contributions can enhance the Z boson pair production cross
sections significantly when the fundamental scale of the large extra
dimensions is up to several TeV. We also show that the kinematic distributions
of the LED signals are greatly different from the standard model ones and the
LHC can probe the values up to TeV at level
depending on the number of the extra dimensions.Comment: Revised version, published in Phys. Rev.
Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass
We present a state-of-the-art calculation of the isovector quark helicity
Bjorken- distribution in the proton using lattice-QCD ensembles at the
physical pion mass. We compute quasi-distributions at proton momenta ~GeV on the lattice, and match them systematically to the
physical parton distribution using large-momentum effective theory (LaMET). We
reach an unprecedented precision through high statistics in simulations,
large-momentum proton matrix elements, and control of excited-state
contamination. The resulting distribution with combined statistical and
systematic errors is in agreement with the latest phenomenological analysis of
the spin-dependent experimental data; in particular, .Comment: 6 pages, 4 figure
Contributions from SUSY-FCNC couplings to the interpretation of the HyperCP events for the decay \Sigma^+ \to p \mu^+ \mu^-
The observation of three events for the decay
with a dimuon invariant mass of MeV by the HyperCP collaboration
imply that a new particle X may be needed to explain the observed dimuon
invariant mass distribution. We show that there are regions in the SUSY-FCNC
parameter space where the in the NMSSM can be used to explain the
HyperCP events without contradicting all the existing constraints from the
measurements of the kaon decays, and the constraints from the
mixing are automatically satisfied once the constraints from kaon decays are
satisfied.Comment: 18 pages, 7 figure
DAMA results at Gran Sasso underground lab
The results obtained with the total exposure of 1.04 ton x yr collected by DAMA/LrBRA-phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are summarized. The DAMA/LLBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton x yr, corresponding to 14 annual cycles) give evidence at 9.3 sigma C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(T1) target. The modulation amplitude of the single-hit events in the (2-6) keV energy interval is: (0.0112 +/- 0.0012) cpd/kg/keV; the measured phase is (144 +/- 7) days and the measured period is (0.998 +/- 0.002) yr, values well in agreement with those expected for DM particles. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. Some of the perspectives of the presently running DAMA/LIBRA-phase2 are outlined
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