126306552
Gluon resummation and QCD corrections to the process p p ---> H0 W
13452281
PROSPECTS OF DISCOVERING THE HIGGS BOSON AT THE TEVATRON
We carry out an event generator based study to evaluate the usefulness of the exclusive signature "e±(μ±) + 2 bottom jets" in discovering the Higgs boson at the Tevatron. Using an event generator, we show that with enough luminosity, one should be able to detect the Higgs boson up to the mass of about 130 GeV. We consider a slightly modified version of the above signature that includes one extra jet. This new signature is more useful because it increases the number of signal events significantly.
119230801
Production of a KK-graviton and a vector boson in ADD model via gluon fusion
A bstractIn the models with large extra-dimensions, we examine the production of a vector boson (γ/ Z) in association with the Kaluza-Klein (KK) modes of the graviton via gluon fusion. At the leading order, the process takes place through quark-loop box and triangle diagrams and it is ultraviolate finite. We report the results for the LHC. We also discuss the issues of anomaly and decoupling of heavy quarks in the amplitude.
55183340
Production of a KK-graviton in association with a boson via gluon fusion at the LHC
We discuss the processes where a KK-graviton ($G$) of the extra-dimensional models is produced in association with a color singlet boson via gluon fusion at the LHC. In particular, we consider the processes $gg \to h G$, $\gamma G$, $Z G$. These processes occur at one-loop through box and triangle diagrams. The cross-section for the process $gg \to \gamma G$ vanishes at the one-loop level. It can be understood by introducing the charge conjugation transformations of the KK-graviton. The processes $gg \to h G$, $Z G$ can be observed at the LHC if the KK-graviton and the Higgs boson exist with appropriate properties.
119181725
Gluon fusion contribution to VHj production at hadron colliders
Abstract We study the associated production of an electroweak vector boson and the Higgs boson with a jet via gluon–gluon fusion. At the leading order, these processes occur at one-loop level. The amplitudes of these one-loop processes are gauge invariant and finite. Therefore, their contributions towards the corresponding hadronic cross sections and kinematic distributions can be calculated separately. We present results for the Large Hadron Collider and its discussed upgrades. We find that the gluon–gluon one-loop process gives dominant contribution to the γHj production. We observe a destructive interference effect in the g g → Z H j amplitude. We also find that in the high transverse momentum and central rapidity region, the ZHj production cross section via gluon–gluon fusion becomes comparable to the cross section contributions coming from quark–quark and quark–gluon channels.
1968264
Production of two photons and a jet through gluon fusion
We have computed the cross-section and distributions for the production of two photons and a jet via the process gg ! g. In the Standard Model, this process occurs at the one-loop level through pentagon and box diagrams. We show that at the LHC this is a signicant mechanism for the production of the two photons and a jet. This process is also an important background to the Higgs boson production, when the Higgs boson decays into two photons. We also explore this process at the Tevatron.
53520410
Leptophilic dark matter and the anomalous magnetic moment of the muon
A bstractWe consider renormalizable theories such that the scattering of dark matter off leptons arises at tree level, but scattering off nuclei only arises at loop. In this framework, the various dark matter candidates can be classified by their spins and by the forms of their interactions with leptons. We determine the corrections to the anomalous magnetic moment of the muon that arise from its interactions with dark matter. We then consider the implications of these results for a set of simplified models of leptophilic dark matter. When a dark matter candidate reduces the existing tension between the standard model prediction of the anomalous magnetic moment and the experimental measurement, the region of parameter space favored to completely remove the discrepancy is highlighted. Conversely, when agreement is worsened, we place limits on the parameters of the corresponding simplified model. These bounds and favored regions are compared against the experimental constraints on the simplified model from direct detection and from collider searches. Although these constraints are severe, we find there do exist limited regions of parameter space in these simple theories that can explain the observed anomaly in the muon magnetic moment while remaining consistent with all experimental bounds.
118791035
Flavored Dark Matter, and Its Implications for Direct Detection and Colliders
We consider theories where the dark matter particle carries flavor quantum numbers, and has renormalizable contact interactions with the Standard Model fields. The phenomenology of this scenario depends sensitively on whether dark matter carries lepton flavor, quark flavor or its own internal flavor quantum numbers. We show that each of these possibilities is associated with a characteristic type of vertex, has different implications for direct detection experiments and gives rise to distinct collider signatures. We find that the region of parameter space where dark matter has the right abundance to be a thermal relic is in general within reach of current direct detection experiments. We focus on a class of models where dark matter carries tau flavor, and show that the collider signals of these models include events with four or more isolated leptons and missing energy. A full simulation of the signal and backgrounds, including detector effects, shows that in a significant part of parameter space these theories can be discovered above Standard Model backgrounds at the Large Hadron Collider. We also study the extent to which flavor and charge correlations among the final state leptons allows models of this type to be distinguished from theories where dark matter couples to leptons but does not carry flavor.
119118344
Improved mass measurement using the boundary of many-body phase space
We show that mass measurements for new particles appearing in decay chains can be improved by determining the boundary of the available phase space in its full dimensionality rather than by using one-dimensional kinematic features for each stage of the cascade decay. This is demonstrated for the case of one particle decaying to three visible and one invisible particles in a two-stage cascade, but our methods also apply to a more general set of decay topologies. We show that not only mass differences but also the overall scale of masses can be determined with high precision without having to rely on cross section information. The improvement arises from the properties of the higher-dimensional phase space itself, independent of the matrix element for the decay, and it is not weakened by the presence of intermediate on-shell particles in the cascade. Our results are particularly significant for the case of low signal statistics, a distinct possibility for new physics searches in the near future.
54542403
Flavored dark matter and the Galactic Center gamma-ray excess
avor-safe manner. We propose a phenomenologically viable model of bottom avored dark matter that can account for the spectral shape and normalization of the gamma-ray excess while naturally suppressing the elastic scattering cross sections probed by direct detection experiments. This model will be denitively tested with increased exposure at LUX and with data from the upcoming high-energy run of the Large Hadron Collider (LHC).
54749102
Lower limits on the strengths of gamma ray lines from WIMP dark matter annihilation
We study the spectra of gamma ray signals that arise from dark matter annihilation in the Universe. We focus on the large class of theories where the photon spectrum includes both continuum spectrum of gamma rays that arise from annihilation into standard model states at tree level, as well as monochromatic gamma rays arising from annihilation directly into two photons at the one-loop level. In this class of theories we obtain lower bounds on the ratio of the strength of the gamma ray line relative to the gamma ray continuum as a function of the dark matter mass and spin. These limits are obtained from the unitarity relation between the tree-level amplitude of the primary annihilation channel and the imaginary part of the loop-level amplitude for annihilation directly into photons, with the primary decay products running in the loop. These results are exact in the limit that dark matter annihilation at tree level is exclusively to a single standard model species, occurs through the lowest partial wave and respects $CP$. Away from this limit the bounds are approximate. Our conclusions agree with known results in the literature for the cases of the minimal supersymmetric standard model, universal extra dimensions and the littlest Higgs with $T$ parity. We use the Fermi-LAT observations to translate these limits into upper bounds on the dark matter annihilation cross section into any specific standard model state.