14264444
MORE SIGNATURES OF THE INTERMEDIATE MASS HIGGS BOSON
We examine the potential signatures of the Higgs boson when it decays into a tau–lepton pair. We show that with the proper identification of the tau-jet, this decay mode can lead to the identification of the Higgs boson over most of the intermediate mass range (MW
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.
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.
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.
54077204
Identifying dark matter interactions in monojet searches
A bstractWe study the discrimination of quark-initiated jets from gluon-initiated jets in monojet searches for dark matter using the technique of averaged jet energy profiles. We demonstrate our results in the context of effective field theories of dark matter interactions with quarks and gluons, but our methods apply more generally to a wide class of models. Different effective theories of dark matter and the standard model backgrounds each have a characteristic quark/gluon fraction for the leading jet. When used in conjunction with the traditional cut-and-count monojet search, the jet energy profile can be used to set stronger bounds on contact interactions of dark matter. In the event of a discovery of a monojet excess at the 14 TeV LHC, contact interactions between dark matter with quarks or with gluons can be differentiated at the 95% confidence level. For a given rate at the LHC, signal predictions at direct detection experiments for different dark matter interactions can span five orders of magnitude. The ability to identify these interactions allows us to make a tighter connection between LHC searches and direct detection experiments.
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.
120513086
Flavored Dark Matter
Title of dissertation: FLAVORED DARK MATTER Prateek Agrawal, Doctor of Philosophy, 2012 Dissertation directed by: Professor Zackaria Chacko Department of Physics Astrophysical observations point to the fact that most of the matter density in the universe is in the form of a non-luminous “dark matter”. No particles detected so far satisfy the criteria to be dark matter candidates. If the present day dark matter density is set by thermal freeze out due to the expansion of the universe, then the dark matter particles likely have weak-scale interactions with ordinary matter. This opens up the possibility of detecting them in current experiments. We focus on a novel class of models – flavored dark matter – which contains multiple copies, or flavors, of dark matter particles, in analogy with the three copies of matter particles observed in nature. We classify such models and consider their implications for various dark matter searches. As an example, we choose one specific model with tau flavored dark matter, and consider its prospects for detection at the Large Hadron Collider. FLAVORED DARK MATTER
118489620
Mixing stops at the LHC
A bstractWe study the phenomenology of a light stop NLSP in the presence of large mixing with either the first or the second generation. R-symmetric models provide a prime setting for this scenario, but our discussion also applies to the MSSM when a significant amount of mixing can be accommodated. In our framework the dominant stop decay is through the flavor violating mode into a light jet and the LSP in an extended region of parameter space. There are currently no limits from ATLAS and CMS in this region. We emulate shape-based hadronic SUSY searches for this topology, and find that they have potential sensitivity. If the extension of these analyses to this region is robust, we find that these searches can set strong exclusion limits on light stops. If not, then the flavor violating decay mode is challenging and may represent a blind spot in stop searches even at 13 TeV. Thus, an experimental investigation of this scenario is well motivated.
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.