15885355
Resumming the color-octet contribution to radiative Upsilon decay
At the upper endpoint of the photon energy spectrum in Upsilon -> X gamma, the standard NRQCD power counting breaks down and the OPE gives rise to color-octet structure functions. Furthermore, in this kinematic regime large Sudakov logarithms appear in the octet Wilson coefficients. The endpoint spectrum can be treated consistently within the framework of a recently developed effective field theory of collinear and soft particles. Here we show that within this approach the octet structure functions arise naturally and that Sudakov logarithms can be summed using the renormalization group equations. We derive an expression for the resummed energy spectrum and, using a model lightcone structure function, investigate the phenomenological importance of the resummation.
117495229
Light gluino and the running of alpha(s)
A gluino in the mass range 12--16 GeV combined with a light (2--5.5 GeV) bottom squark, as has been proposed recently to explain an excess of b quark hadroproduction, would affect the momentum-scale dependence (``running'') of the strong coupling constant alpha_s in such a way as to raise its value at M_Z by about 0.014 +/- 0.001. If one combines sources of uncertainty at low (m_b) and high (M_Z) mass scales, one can only distinguish such an effect at slightly more than the 2 sigma level. Prospects for improvement in this situation, which include better lattice QCD simulations and better measurements at M_Z, are discussed.
118094398
Determining the Unitarity Triangle from Two‐Body Charmless Hadronic B Decays
We performed an updated global fits to charmless Bu,d → PP decays in the framework of flavor SU(3) symmetry, without referring to sin2β measured from the charmonium decay modes. Fit results directly constrain the (ρ, η) vertex of the unitarity triangle. Details regarding the analyses of different schemes of SU(3) breaking in decay amplitude sizes and predictions for the branching ratios and CP asymmetries of Bu,d,s → PP decays are given in Ref. [1].
119255219
Partially strong WW scattering
What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the WW scattering. After partial unitarization by the light Higgs boson, the WW scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong WW scattering.
119207675
Phenomenology of large mixing for the CP-even neutral scalars of the Higgs triplet model
The Higgs triplet model contains two CP-even neutral scalar eigenstates, each having components from an isospin doublet and an isospin triplet scalar field. The mixing angle can be maximal if the masses of the scalar eigenstates are close to degeneracy. We quantify the dependence of the mixing angle on the mass splitting and on the vacuum expectation value of the neutral triplet scalar. We determine the parameter space for maximal mixing, and study the observability of both CP-even Higgs bosons at the CERN LHC.
96443947
Discovery in Drell-Yan processes at the LHC
We study the Drell-Yan process mediated by a new bosonic resonance at the LHC. The bosons of spin-0, 1, and 2 with the most general leading-order couplings to standard model fermions and gluons are considered, which provides a model-independent formulation for future exploration of the resonance properties, such as its spin, mass and couplings. In the case of neutral resonances, we demonstrate how the shapes of the kinematical distributions change as one varies the chiral couplings of the quarks and leptons, and show how to analyze the couplings by making use of the forward-backward asymmetry. In the case of charged resonances, we propose a novel technique to effectively reconstruct the angular distribution in the center-of-mass frame, to a large extent avoiding the two-fold ambiguity due to the missing neutrino. Similar to the case of a neutral resonance, the spin information of the resonance can be extracted unambiguously, and chiral couplings and the asymmetries can be explored in a statistical manner. With the current LHC data, we present bounds on the mass and cross section times branching fraction of the new resonance and estimate the future reach.
54957266
Constraining the detailed balance condition in Hořava gravity with cosmic accelerating expansion
In 2009 Hořava proposed a power-counting renormalizable quantum gravity theory. Afterwards a term in the action that softly violates the detailed balance condition has been considered with the attempt of obtaining a more realistic theory in its IR-limit. This term is proportional to ωR(3), where ω is a constant parameter and R(3) is the spatial Ricci scalar. In this paper we derive constraints on this IR-modified Hořava theory using the late-time cosmic accelerating expansion observations. We obtain a lower bound of |ω| that is nontrivial and depends on ΛW, the cosmological constant of the three dimensional spatial action in the Hořava gravity. We find that to preserve the detailed balance condition, one needs to fine-tune ΛW such that −2.29 × 10−4 < (c2ΛW)/(H20ΩDE)−2 < 0, where H0 and ΩDE are the Hubble parameter and dark energy density fraction in the present epoch, respectively. On the other hand, if we do not insist on the detailed balance condition, then the valid region for ΛW is much relaxed to −0.39 < (c2ΛW)/(H20ΩDE)−2 < 0.12. We find that although the detailed balance condition cannot be ruled out, it is strongly disfavored.
119227092
Dark matter detection with polarized detectors
Abstract We consider the prospects to use polarized dark-matter detectors to discriminate between various dark-matter models. If WIMPs are fermions and participate in parity-violating interactions with ordinary matter, then the recoil-direction and recoil-energy distributions of nuclei in detectors will depend on the orientation of the initial nuclear spin with respect to the velocity of the detector through the Galactic halo. If, however, WIMPS are scalars, the only possible polarization-dependent interactions are extremely velocity-suppressed and, therefore, unobservable. Since the amplitude of this polarization modulation is fixed by the detector speed through the halo, in units of the speed of light, exposures several times larger than those of current experiments will be required to be probe this effect.