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.
119201106
Semi-direct Gauge-Yukawa mediation
We propose semi-direct Gauge-Yukawa mediation of supersymmetry (SUSY) breaking. The messenger fields mediating SUSY breaking to the visible sector do not directly couple with the goldstino field, and instead they have gauge and Yukawa interactions with some primary messenger fields which couple directly with the goldstino fields. From the explicit Feynman diagram calculations for the SUSY breaking soft masses, we find that the SUSY particle spectra can be realistic. Especially, this generalization of semi-direct gauge mediation solves the massless gaugino mass problem since the holomorphic soft mass terms of the messenger fields can be generated by Yukawa couplings. We also provide some arguments that this scenario can be realized naturally in some dynamical SUSY-breaking models such as the ISS-like model.
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.
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.
118418532
Nuclear modification of high transverse momentum particle production in p + A collisions at RHIC and LHC
Abstract We present results and predictions for the nuclear modification of the differential cross sections for inclusive light hadron and prompt photon production in minimum bias d + Au collisions at s = 200 GeV and minimum bias p + Pb collisions at s = 5 TeV at RHIC and LHC, respectively. Our calculations combine the leading order perturbative QCD formalism with cold nuclear matter effects that arise from the elastic, inelastic and coherent multiple scattering of partons in large nuclei. We find that a theoretical approach that includes the isospin effect, Cronin effect, cold nuclear matter energy loss and dynamical shadowing can describe the RHIC d + Au data rather well. The LHC p + Pb predictions will soon be confronted by new experimental results to help clarify the magnitude and origin of cold nuclear matter effects and facilitate precision dense QCD matter tomography.
119259319
QCD evolution of the Sivers asymmetry
We study the QCD evolution of the Sivers effect in both semi-inclusive deep inelastic scattering (SIDIS) and Drell-Yan production (DY). We pay close attention to the nonperturbative spin-independent Sudakov factor in the evolution formalism and find a universal form which can describe reasonably well the experimental data on the transverse momentum distributions in SIDIS, DY lepton pair and W/Z production. With this Sudakov factor at hand, we perform a global fitting of all the experimental data on the Sivers asymmetry in SIDIS from HERMES, COMPASS and Jefferson Lab. We then make predictions for the Sivers asymmetry in DY lepton pair and W production that can be compared to the future experimental measurements to test the sign change of the Sivers functions between SIDIS and DY processes and constrain the sea quark Sivers functions. © 2014 American Physical Society.
118412729
Evolution of twist-3 multiparton correlation functions relevant to single transverse-spin asymmetry
We construct two sets of twist-3 correlation functions that are responsible for generating the novel single transverse-spin asymmetry in the QCD collinear factorization approach. We derive evolution equations for these universal three-parton correlation functions. We calculate evolution kernels relevant to the gluonic pole contributions to the asymmetry at the order of {alpha}{sub s}. We find that all evolution kernels are infrared safe as they should be and have a lot in common with the Dokshitzer-Gribov-Lipatov-Alterelli-Parisi evolution kernels of unpolarized parton distributions. By solving the evolution equations, we explicitly demonstrate the factorization scale dependence of these twist-3 correlation 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.
119873813
Factorization and Quarkonium Production
It is possible to extend the formalism for high- p T heavy quarkonium factorization beyond leading power. This extension may be helpful in interpreting the relative roles of octet and singlet channels in the formalism of nonrelativistic QCD (NRQCD). It may enable us to understand the origin of the surprisingly large results for cross sections calculated in the color singlet sector of NRQCD.