Large Kinematic Region Research Articles

Multipartite dark matter in SU(2)N extension of Standard Model and signatures at the LHC

An SU(2)N extension (N stands for neutral) of the Standard Model (SM) is proposed with an additional U(1) = S′ global symmetry, which stabilizes the lightest of the vector boson (X,X̄) as dark matter (DM) through unbroken S = T3N+S′. The field content of the model is motivated to address neutrino mass generation, a possible unification to SU(7), along with spontaneous symmetry breaking of SU(2)N resulting in massive gauge bosons. None of the SM particles are charged under SU(2)N and therefore X,X̄ do not have a direct coupling to the visible sector besides a Higgs portal, which is tiny to avoid any conflict with Higgs data. We show that, a large kinematic region of this model allows the neutral component of SU(2)N scalar triplet and heavy neutrinos introduced here to become additional DM components. In this paper we explore the viability of such multipartite DM parameter space, including non-zero DM-DM interactions, to comply with relic density and direct search constraints. We also demonstrate that the model may yield hadronically quiet single lepton and two lepton signatures with missing energy at the Large Hadron Collider (LHC) that can be accessed with high luminosity.

Spin physics at IHEP

IHEP has rich program devoted to the spin physics studies. New experimental program will significantly increase the number of reaction investigated at large kinematic region. The experiment will measure different polarization variables in inclusive and exclusive reactions, including single- and double-spin asymmetry, polarization, spin transfer parameters. One of the most important task is the creation of the polarized beam and especially polarized anti-proton beam.

Excess of continuum dimuon production at masses between threshold and the $J/\Psi$ in S–W interactions at 200 GeV $/c$ /nucleon

Results are presented on dimuon production for invariant masses ranging from the dimuon threshold up to the $J/\Psi$ meson. Proton-tungsten and sulphur-tungsten interactions at 200 GeV $/c$ /nucleon were measured over a large kinematic region, using the HELIOS/3 dimuon spectrometer at the CERN SPS. In the continuum regions between the dimuon threshold and the $\rho/\omega$ mesons, and between the $\phi$ and $J/\Psi$ mesons, an excess is observed in S–W interactions relative to minimum bias p–W interactions. The observed excess is continuous over the explored mass range and has no apparent resonant structure. In the low mass region the dimuon yield increases by $(76\pm 4)$ % of the corresponding p–W dimuon spectrum, whereas in the higher mass region the excess amounts to $2.4\pm 0.3$ times the p–W yield. The observed excess for the low mass region follows an exponential transverse mass distribution with an average inverse slope parameter T of $(190\pm5)$ MeV $/c^2$ , constant for all but the lowest charged multiplicity interval and consistent with the slope of the excess in the higher mass region. In the invariant mass range of 1.35–2.5 GeV $/c^2$ the continuum dimuon mass distribution observed in p–W interactions can be quantitatively understood as a sum of three expected contributions (vector meson decays, semileptonic charm decays and Drell-Yan process), but both in central and in minimum bias S–W interactions an excess is observed with respect to these sources which does not depend on centrality, nor very strongly on the transverse momentum.

Excess of continuum dimuon production at masses between threshold and the

Results are presented on dimuon production for invariant masses ranging from the dimuon threshold up to the $J/\Psi$ meson. Proton-tungsten and sulphur-tungsten interactions at 200 GeV $/c$ /nucleon were measured over a large kinematic region, using the HELIOS/3 dimuon spectrometer at the CERN SPS. In the continuum regions between the dimuon threshold and the $\rho/\omega$ mesons, and between the $\phi$ and $J/\Psi$ mesons, an excess is observed in S–W interactions relative to minimum bias p–W interactions. The observed excess is continuous over the explored mass range and has no apparent resonant structure. In the low mass region the dimuon yield increases by $(76\pm 4)$ % of the corresponding p–W dimuon spectrum, whereas in the higher mass region the excess amounts to $2.4\pm 0.3$ times the p–W yield. The observed excess for the low mass region follows an exponential transverse mass distribution with an average inverse slope parameter T of $(190\pm5)$ MeV $/c^2$ , constant for all but the lowest charged multiplicity interval and consistent with the slope of the excess in the higher mass region. In the invariant mass range of 1.35–2.5 GeV $/c^2$ the continuum dimuon mass distribution observed in p–W interactions can be quantitatively understood as a sum of three expected contributions (vector meson decays, semileptonic charm decays and Drell-Yan process), but both in central and in minimum bias S–W interactions an excess is observed with respect to these sources which does not depend on centrality, nor very strongly on the transverse momentum.

Study of vector mesons in dimuon production in a large kinematic region in p-W and S-W interactions at 200 GeV/c/nucleon

Results are presented on p + ω,o and J/ψ production in p-W and 32S-W interactions at 200GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio Bσo/ (Bσρ + Bσω), where B is the relevant resonance µµ branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S-W interactions. This results from an increase in the number of produced o’s per charged particle. The ratio is measured in different intervals of pt and rapidity. It is not clearly dependent on pt, but is larger at higher rapidities. J/Ψ production, likewise normalized to charged multiplicity, is significantly lower in S-W compared to p-W interactions.

Study of vector mesons in dimuon production in a large kinematic region in p–W and S–W interactions at 200 GeV/c/nucleon

Results are presented on p + ω,ø and J/ψ production in p-W and 32S-W interactions at 200GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio Bσø/ (Bσρ + Bσω), where B is the relevant resonance µµ branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S-W interactions. This results from an increase in the number of produced ø’s per charged particle. The ratio is measured in different intervals of pt and rapidity. It is not clearly dependent on pt, but is larger at higher rapidities. J/Ψ production, likewise normalized to charged multiplicity, is significantly lower in S-W compared to p-W interactions.

Charged particle multiplicities in deep inelastic scattering at HERA

Using the H1 detector at HERA, charged particle multiplicity distributions in deep inelastice + p scattering have been measured over a large kinematical region. The evolution withW andQ 2 of the multiplicity distribution and of the multiplicity moments in pseudorapidity domains of varying size is studied in the current fragmentation region of the hadronic centre-of-mass frame. The results are compared with data from fixed target lepton-nucleon interactions,e + e − annihilations and hadron-hadron collisions as well as with expectations from QCD based parton models. Fits to the Negative Binomial and Lognormal distributions are presented.

Coherent pion-photoproduction by deuterons at intermediate energies

Non-relativistically exact single scattering calculations for coherent pion photoproduction by deuterons at intermediate photon energies (200 MeV to 500 MeV) are presented. For the two-bodyγN→πN process we use the well-known dispersion theoretic model by Chewet al and for the deuteron wave-functions we employ the Yamaguchi and the two term Gaussian wave-function. We find that while both the wavefunctions reproduce the deuteron e.m. form factor reasonably well, the results for the pion photoproduction cross-section show, however, a sensitive dependence on their detailed forms. The angular distributions at various energies are found to have considerable variations from the usual impulse approximation calculations but tend to improve the agreement with the data in a large kinematical region.

Coherent photoproduction of the πO meson on deuterium

The differential cross section of the reaction γD → π O D has been measured at constant omentum transfer, using a counter technique, in a large kinematical region, ranging from 240 MeV/ c to 1000 MeV/ c momentum transfer and from 220 MeV to 1400 MeV lab proton energy.