118726740
Single transverse-spin asymmetry for D -meson production in semi-inclusive deep inelastic scattering
We study the single transverse-spin asymmetry for open charm production in the semi-inclusive lepton-hadron deep inelastic scattering. We calculate the asymmetry in terms of the QCD collinear factorization approach for D mesons at high enough P{sub hperpendicular} and find that the asymmetry is proportional to the twist-three trigluon correlation function in the proton. With a simple model for the trigluon correlation function, we estimate the asymmetry for both COMPASS and eRHIC kinematics and discuss the possibilities of extracting the trigluon correlation function in these 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.
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.
119220033
Global fitting of single spin asymmetry: an attempt
We present an attempt of global analysis of Semi-Inclusive Deep Inelastic Scattering (SIDIS) $$\ell p^\uparrow \to \ell' \pi X$$ data on single spin asymmetries and data on left-right asymmetry $A_N$ in $$p^\uparrow p \to \pi X$$ in order to simultaneously extract information on Sivers function and twist-three quark-gluon Efremov-Teryaev-Qiu-Sterman (ETQS) function. We explore different possibilities such as node of Sivers function in $x$ or $$k_\perp$$ in order to explain ``sign mismatch'' between these functions. We show that $$\pi^\pm$$ SIDIS data and $$\pi^0$$ STAR data can be well described in a combined TMD and twist-3 fit, however $$\pi^\pm$$ BRAHMS data are not described in a satisfactory way. This leaves open a question to the solution of the ``sign mismatch''. Possible explanations are then discussed.
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.
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.
118390932
Decaying dark matter in the supersymmetric standard model with freeze-in and seesaw mechanims
Inspired by the decaying dark matter (DM) which can explain cosmic ray anomalies naturally, we consider the supersymmetric Standard Model with three right-handed neutrinos (RHNs) and R-parity, and introduce a TeV-scale DM sector with two fields ϕ1,2 and a Z3 discrete symmetry. The DM sector only interacts with the RHNs via a very heavy field exchange and then we can explain the cosmic ray anomalies. With the second right-handed neutrino N2 dominant seesaw mechanism at the low scale around 104 GeV, we show that ϕ1,2 can obtain the vacuum expectation values around the TeV scale, and then the lightest state from ϕ1,2 is the decay DM with lifetime around ∼1026s. In particular, the DM very long lifetime is related to the tiny neutrino masses, and the dominant DM decay channels to μ (and τ) are related to the approximate μ − τ symmetry. Furthermore, the correct DM relic density can be obtained via the freeze-in mechanism, the small-scale problem for power spectrum can be solved due to the decays of the R-parity odd meta-stable states in the DM sector, and the baryon asymmetry can be generated via the soft leptogensis.
118503601
Brightening the (130 GeV) Gamma-Ray Line
The gamma-ray line from dark matter (DM) annihilation is too weak to observe, but its observation will uncover much information, e.g., the DM mass and an anomalously large annihilation rate ∼ 0.1 pb into di-photon. In this work, we construct a minimal effective theory (EFT) incorporating DM and heavier charged particles. A large annihilation rate is obtained from operator coefficients with resonance or strong coupling enhancement.The EFT is stringently constrained by the XENON100 and WMAP data. Without resonance, Dirac DM or colored charged particles are ruled out. It is pointed out that the di-gluon mode may correctly determine the DM relic density. Interestingly, this framework also provides an origin for the Higgs di-photon excess at the LHC. We apply the general analysis to the NMSSM, which can elegantly interpret the tentative 130 GeV gamma-ray line. A top-window model is also proposed to explain the gamma-ray line.
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.
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.
118563295
Origins of the isospin violation of dark matter interactions
Light dark matter (DM) with a large DM-nucleon spin-independent scattering cross section and moreover proper isospin violation (ISV) f(n)/f(p) approximate to -0.7 may provide a way to understand the confusing DM.)M direct detection results. Further using the stringent astrophysical and collider constraints, we systematically investigate the origin of ISV,T first via general operator analyses and further via specifying three types of mediators: a light Z ' from chiral U(1)(x), an approximate spectator Higgs doublet (It can explain the W + jj anomaly simultaneously) and color triplets. In addition, although Z' from an exotic U(1)(x) mixing with U(1)(Y) generates only f(n) = 0, we can combine it with the conventional to achieve the proper ISV. As a concrete example, we propose the U(1)(x) model where the U(1)(x) charged light sneutrino is an inelastic DM, which dominantly annihilates to light dark states such as Z' with sub-GeV mass. The model can consistently (with other DM direct detection results) and safely interpret the recent GoGeNT annual modulation result.