122943004
Looking for a higgs boson of intermediate mass
Abstract It is pointed out that the ability to identify and reconstruct bottoms jets will be important for the identification of the Higgs boson at hadron colliders, if its mass is in the intermediate mass range (2 M W > M H > M Z ). We examine a particular tagging scheme.
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.
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.
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.
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.
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.
116347830
Direct Detection Constraints on Dark Matter Event Rates in Neutrino Telescopes, and Collider Implications
Neutrino telescopes are looking to detect neutrinos produced by the annihilation of weakly interacting massive particle (WIMP) dark matter in the sun. The event rate depends on the dark matter density in the sun, which in turn is dictated by the cross section of WIMPs with nucleons. This however is bounded by direct detection experiments. We use the constraints from these experiments to place model-independent upper bounds on the event rates in neutrino telescopes that apply to any elastic dark matter model. Since the spin-independent WIMP-nucleon cross section is much more tightly constrained than the corresponding spin-dependent cross section, the bounds are much stronger in the former case and are competitive with the current limits from IceCube. If the number of events observed in neutrino telescopes exceeds the upper bound corresponding to spin-independent interactions, the implication is that the cross section of dark matter with nucleons is dominated by spin- dependent interactions. In such a scenario the natural dark matter candidates are Majorana fermions and real vector bosons, so that dark matter particles are their own anti-particles. We show that any such theory that leads to observable event rates at current generation neutrino telescopes will in general contain new particles charged under the Standard Model gauge groups that naturally lie in a mass range that is kinematically accessible to the Large Hadron Collider (LHC).
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.
117007207
A Classification of Dark Matter Candidates with Primarily Spin-Dependent Interactions with Matter
We perform a model-independent classification of Weakly Interacting Massive Particle (WIMP) dark matter candidates that have the property that their scattering off nucleons is dominated by spin-dependent interactions. We study renormalizable theories where the scattering of dark matter is elastic and arises at tree-level. We show that if the WIMP-nucleon cross section is dominated by spin-dependent interactions the natural dark matter candidates are either Majorana fermions or real vector bosons, so that the dark matter particle is its own anti-particle. In such a scenario, scalar dark matter is disfavored. Dirac fermion and complex vector boson dark matter are also disfavored, except for very specific choices of quantum numbers. We further establish that any such theory must contain either new particles close to the weak scale with Standard Model quantum numbers, or alternatively, a $Z'$ gauge boson with mass at or below the TeV scale. In the region of parameter space that is of interest to current direct detection experiments, these particles naturally lie in a mass range that is kinematically accessible to the Large Hadron Collider (LHC).
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.
119357132
The phenomenology of lepton flavored dark matter
In Flavored Dark Matter theories 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. For the lepton flavored case, we investigate the implications for direct detection experiments and collider signatures. We show that the region of parameter space which leads to the right abundance for a thermal relic is in general within reach of current direct detection experiments. Focusing on a class of models where dark matter carries tau flavor, we show 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...