118400039
Single transverse spin asymmetry of dilepton production near Z 0 pole
Using the latest quark Sivers functions extracted from the global analysis of available data on single transverse spin asymmetry (SSA), we calculate the SSA of Drell-Yan inclusive production of lepton pairs of invariant mass Q at both 4<Q<9 GeV and Q{approx}M{sub Z} in p{sup {up_arrow}p} collisions at Relativistic Heavy Ion Collider energies. We find that the features of the asymmetry A{sub N} for Q{approx}M{sub Z} are significantly different from that when 4<Q<9 GeV. The A{sub N} near Z{sup 0} pole is positive and sizable in the central rapidity region, while the A{sub N} at low Q is negative and only sizable in the forward rapidity region. We show that the size of A{sub N} is sufficiently large for a wide range of Q around the Z{sup 0} pole, and even with the lepton pair's invariant mass integrated from Q=70 GeV to 110 GeV, the A{sub N} is still close to 10% for the central and near forward rapidity region. We argue that the SSAs of Drell-Yan inclusive dilepton production at low Q, and that near the Z{sup 0} pole, provide complementary information for testing the time-reversal modified universality (the sign change) of the Sivers functions.
119264976
Inclusive b-jet production in heavy ion collisions at the LHC
Abstract Theoretical and experimental advances in understanding light jet production and modification in Pb + Pb reactions at s N N = 2.76 TeV have been a highlight of the LHC heavy ion program. At the same time, the detailed mechanisms of heavy quark propagation and energy loss in dense QCD matter are not yet fully understood. With this motivation, we present theoretical predictions for the nuclear-induced attenuation of the differential cross section for inclusive b-jet production in heavy ion collisions at the LHC for comparison to upcoming data. We find that for transverse momenta p T ≳ 75 GeV both hadronization and mass effects are negligible and this attenuation is comparable to the one observed for light jets. We discuss how the detailed b-jet quenching patterns can be used to gain new insight into the in-medium heavy flavor dynamics.
18844875
Indication on the process dependence of the Sivers effect.
We analyze the spin asymmetry for single inclusive jet production in proton-proton collisions collected by the AnDY experiment at the Relativistic Heavy Ion Collider and the Sivers asymmetry data from semi-inclusive deep inelastic scattering experiments. In particular, we consider the role color gauge invariance plays in determining the process dependence of the Sivers effect. We find that after carefully taking into account the initial-state and final-state interactions between the active parton and the remnant of the polarized hadron, the calculated jet spin asymmetry based on the Sivers functions extracted from HERMES and COMPASS experiments is consistent with the AnDY experimental data. This provides a first indication for the process dependence of the Sivers effect in these processes. We also make predictions for both direct photon and Drell-Yan spin asymmetry, to further test the process dependence of the Sivers effect in future experiments.
120322546
Process Dependence and the Sivers Effect in Inclusive and Semi-Inclusive Reactions
We perform an analysis of the the spin asymmetry for single inclusive jet production in proton-proton collisions collected by AnDY experiment and the Sivers asymmetry data from semi-inclusive deep inelastic scattering experiments. In particular, we consider the role color gauge invariance plays in determining the process-dependence of the Sivers effect. We find that after carefully taking into account the initial-state and final-state interactions between the active parton and the remnant of the polarized hadron, the calculated jet spin asymmetry based on the Sivers functions extracted from HERMES and COMPASS experiments is consistent with the AnDY experimental data. This provides a first indication for the process-dependence of the Sivers effect in different processes. We also make predictions for both direct photon and Drell-Yan spin asymmetry, to further test the process-dependence of the Sivers effect in future experiments.
49273245
Quark-gluon correlation functions relevant to single transverse spin asymmetries
We investigate the relative size of various twist-3 quark-gluon correlation functions relevant to single transverse spin asymmetries (SSAs) in a quark-diquark model of the nucleon. We calculate the quark-gluon correlation function T{sub q,F}(x,x) that is responsible for the gluonic pole contribution to the SSAs, as well as T{sub q,F}(0,x) and T{sub {Delta}q,F}(0,x) responsible for the fermionic pole contributions. We find in both cases of a scalar diquark and an axial-vector diquark that at the first nontrivial order only the T{sub q,F}(x,x) is finite while all other quark-gluon correlation functions vanish. Using the same model, we evaluate quark Sivers function and discuss its relation to the T{sub q,F}(x,x). We also discuss the implication of our finding to the phenomenological studies of the SSAs.
119193850
Exploring the structure of the proton through polarization observables in lp→jet X
We present results for a complete set of polarization observables for jet production in lepton-proton collision, where the final-state lepton is not observed. The calculations are carried out in collinear factorization at the level of Born diagrams. For all the observables we also provide numerical estimates for typical kinematics of a potential future electron-ion collider. On the basis of this numerical study, the prospects for the transverse single target spin asymmetry are particularly promising. This observable is given by a certain quark-gluon correlation function, which has a direct relation to the transverse momentum dependent Sivers parton distribution.
118656803
Realistic flipped SU(5) from orbifold SO(10)
We propose a realistic flipped SU(5) model derived from a five-dimensional orbifold SO(10) model. The Standard Model (SM) fermion masses and mixings are explained by combining the traditional Froggatt-Nielsen mechanism with the five-dimensional wave function profiles of the SM fermions. Employing tree-level spontaneous R-symmetry breaking in the hidden sector and extra(ordinary) gauge mediation, we obtain realistic supersymmetry breaking soft mass terms with non-vanishing gaugino masses. Including the messenger fields at the intermediate scale and Kaluza-Klein states at the compactification scale, we study gauge coupling unification. We show that the SO(10) unified gauge coupling is very strong and the unification scale can be much higher than the compactification scale. We briefly discuss proton decay as well.
118390410
Light dark matter from the U(1)(X) sector in the NMSSM with gauge mediation
Cosmic ray anomalies observed by PAMELA and Fermi-LAT experiments may be interpreted by heavy (TeV-scale) dark matter annihilation enhanced by Sommerfeld effects mediated by a very light (sub-GeV) U(1)(X) gauge boson, while the recent direct searches from CoGeNT and DAMA/LIBRA experiments may indicate a rather light (similar to 7GeV) dark matter with weak interaction. Motivated by these apparently different scales, we consider a gauge mediated next-to-the minimal supersymmetric standard model (NMSSM) entended with a light U(1)(X) sector plus a heavy sector ((H) over barh, Hh), which can provide both a light (similar to 7GeV) and a heavy (TeV-scale) dark matter without introducing any ad hoc new scale. Through the Yukawa coupling between Hh and the messager fields, the U(1)(X) gauge symmetry is broken around the GeV scale radiatively and a large negative m(S)(2) is generated for the NMSSM singlet S. Furthermore, the small kinetic mixing parameter between U(1)(X) and U(1)(Y) is predicted to be theta similar to 10(-5) - 10(-6) after integrating out the messengers. Such a light dark matter, which can have a normal relic density from the late decay of the right-handed sneutrino (assumed to be the ordinary next-to-the lightest supersymmetric particle and thermally produced in the early Universe), can serve a good candidate to explain the recent CoGeNT and DAMA/LIBRA results.
119216010
Asymmetric origin for gravitino relic density in the hybrid gravity-gauge mediated supersymmetry breaking
A bstractWe propose the hybrid gravity-gauge mediated supersymmetry breaking where the gravitino mass is about several GeV. The strong constraints on supersymmetry viable parameter space from the CMS and ATLAS experiments at the LHC can be relaxed due to the heavy colored supersymmetric particles, and it is consistent with null results in the dark matter (DM) direct search experiments such as XENON100. In particular, the possible maximal flavor and CP violations from the relatively small gravity mediation may naturally account for the recent LHCb anomaly. In addition, because the gravitino mass is around the asymmetric DM mass, we propose the asymmetric origin of the gravitino relic density and solve the cosmological coincident problem on the DM and baryon densities ΩDM : ΩB ≈ 5 : 1. The gravitino relic density arises from asymmetric metastable particle (AMP) late decay. However, we show that there is no AMP candidate in the minimal supersymmetric Standard Model (SM) due to the robust gaugino/Higgsino mediated wash-out effects. Interestingly, AMP can be realized in the well motivated supersymmetric SMs with vector-like particles or continuous U(1)R symmetry. Especially, the lightest CP-even Higgs boson mass can be lifted in the supersymmetric SMs with vector-like particles.
119234621
A Rediatively Light Stop Saves the Best Global Fit for Higgs Boson Mass and Decays
The LHC discovered the Standard Model (SM) like Higgs boson with mass around 125 GeV. However, there exist hints of deviations from Higgs decays. Including the Tevatron data, the deviations can be explained by the extremely mixed stop sector in the sense of best global fit (BGF). We analyze the relations among the competing reduced coupling hGG, Higgs boson mass,and LHC stop mass m_{\wt t_1} lower bound at the tree- and one-loop level. In particular, we point out that we use the light stop running mass in the Higgs boson mass calculation while the light stop pole mass in the Higgs decays. So the gluino radiative correction on the light stop mass plays the crucial role. Its large negative correction saves the GBF in the Minimal Supersymmetric SM (MSSM) and the next to the MSSM (NMSSM) constrained by the perturbativity. Moreover, a light stop is predicted: in the MSSM if we set the gluino mass M_3\lesssim4 TeV, we have m_{\wt t_1}<m_t; while in the NMSSM, imposing the least tuning condition we get m_{\wt t_1}\simeq130 GeV for M_3\simeq1.5 TeV.
119232543
On naturalness of the MSSM and NMSSM
A bstractWith a bottom-up approach, we consider naturalness in the MSSM and NMSSM. Assuming the light stops, the LHC gluino search implies that the degree of fine tuning in both models is less than 2.5%. Taking the LHC hints for the SM-like Higgs boson mass mh ~ 125 GeV seriously, we find that naturalness will favor the NMSSM. We study the Higgs boson mass for several scenarios in the NMSSM: (1) A large λ and the doublet-singlet Higgs boson mixing effect pushing upward or pulling downward mh. The former case can readily give the di-photon excess of the Higgs boson decay whereas the latter case can not. However, we point out that the former case has a new large fine-tuning related to strong λ−RGE running effect and vacuum stability. (2) A small λ and the mixing effect pushing mh upward. Naturalness status becomes worse and no significant di-photon excess can be obtained. In these scenarios, the lightest supersymmetric particle (LSP) as a dark matter candidate is strongly disfavored by the XENON100 experiment. Even if the LSP can be a viable dark matter candidate, there does exist fine-tuning. The above naturalness evaluation is based on a high mediation scale for supersymmetry breaking, whereas for a low mediation scale, fine-tuning can be improved by about one order.