Baris Altunkaynak

Higgs boson mass predictions in supergravity unification, recent LHC-7 results, and dark matter

LHC-7 has narrowed down the mass range of the light Higgs boson. This result is consistent with the supergravity unification framework, and the current Higgs boson mass window implies a rather significant loop correction to the tree value pointing to a relatively heavy scalar sparticle spectrum with universal boundary conditions. It is shown that the largest value of the Higgs boson mass is obtained on the Hyperbolic Branch of radiative breaking. The implications of light Higgs boson in the broader mass range of 115 GeV to 131 GeV and a narrower range of 123 GeV to 127 GeV are explored in the context of the discovery of supersymmetry at LHC-7 and for the observation of dark matter in direct detection experiments.

Solving the LHC Inverse Problem with Dark Matter Observations

We investigate the utility of cosmological and astrophysical observations for distinguishing between supersymmetric theories. In particular we consider 276 pairs of models that give rise to nearly identical patterns of observables at hadron colliders. We focus attention on neutralino scattering experiments (direct detection of relic neutralinos) and observations of gamma-rays from relic neutralino annihilation (indirect detection experiments). Both classes of experiments planned for the near future will make measurements with exceptional precision. In principle, therefore, they will have the ability to be surprisingly effective at discriminating between candidate theories. However, the ability to distinguish between models will be highly dependent on future theoretical progress on such things as determination of the local halo density model and uncertainty in nuclear matrix elements associated with neutralino recoil events. If one imagines perfect knowledge of these theoretical inputs, then with extremely conservative physics assumptions and background estimates we find 101 of the 276 degenerate pairs can be distinguished. Using slightly more optimistic assumptions about background rates increases this number to 186 of the 276 pairs. We discuss the sensitivity of these results to additional assumptions made about nuclear matrix elements, the cosmological density of neutralinos and the galactic halo profile. We also comment on the complementarity of this study to recent work investigating these same pairs at a (s)1/2 = 500?GeV linear collider.

Flavor changing heavy Higgs interactions at the LHC

Abstract A general two Higgs doublet model (2HDM) is adopted to study the signature of flavor changing neutral Higgs (FCNH) decay ϕ 0 → t c ¯ + t ¯ c , where ϕ 0 could be a CP-even scalar ( H 0 ) or a CP-odd pseudoscalar ( A 0 ). Measurement of the light 125 GeV neutral Higgs boson ( h 0 ) couplings at the Large Hadron Collider (LHC) favor the decoupling limit or the alignment limit of a 2HDM, in which gauge boson and diagonal fermion couplings of h 0 approach Standard Model values. In such limit, FCNH couplings of h 0 are naturally suppressed by a small mixing parameter cos ⁡ ( β − α ) , while the off-diagonal couplings of heavier neutral scalars ϕ 0 are sustained by sin ⁡ ( β − α ) ∼ 1 . We study physics background from dominant processes with realistic acceptance cuts and tagging efficiencies. Promising results are found for the LHC running at 13 or 14 TeV collision energies.

Supersymmetric discovery potential and benchmarks for early runs at √s=7 TeV at the LHC

We carry out an analysis of the potential of the Large Hadron Collider (LHC) to discover supersymmetry in runs at {radical}(s)=7 TeV with an accumulated luminosity of (0.1-2) fb{sup -1} of data. The analysis is done with both minimal supergravity and supergravity models with nonuniversal soft breaking. Benchmarks for early discovery with (0.1-2) fb{sup -1} of data are given. We provide an update of b-tagging efficiencies in PGS 4 appropriate for LHC analyses. A large number of signature channels are analyzed, and it is shown that each of the models exhibited are discoverable at the 5{sigma} level or more above the standard model background in several signature channels which would provide cross checks for a discovery of supersymmetry. It is shown that some of the benchmarks are discoverable with 0.1 fb{sup -1} of data again with detectable signals in several channels.

Sparticle mass hierarchies, simplified models from SUGRA unification, and benchmarks for LHC Run-II SUSY searches

A bstractSparticle mass hierarchies contain significant information regarding the origin and nature of supersymmetry breaking. The hierarchical patterns are severely constrained by electroweak symmetry breaking as well as by the astrophysical and particle physics data. They are further constrained by the Higgs boson mass measurement. The sparticle mass hierarchies can be used to generate simplified models consistent with the high scale models. In this work we consider supergravity models with universal boundary conditions for soft parameters at the unification scale as well as supergravity models with nonuniversalities and delineate the list of sparticle mass hierarchies for the five lightest sparticles. Simplified models can be obtained by a truncation of these, retaining a smaller set of lightest particles. The mass hierarchies and their truncated versions enlarge significantly the list of simplified models currently being used in the literature. Benchmarks for a variety of supergravity unified models appropriate for SUSY searches at future colliders are also presented. The signature analysis of two benchmark models has been carried out and a discussion of the searches needed for their discovery at LHC Run-II is given. An analysis of the spin-independent neutralino-proton cross section exhibiting the Higgs boson mass dependence and the hierarchical patterns is also carried out. It is seen that a knowledge of the spin-independent neutralino-proton cross section and the neutralino mass will narrow down the list of the allowed sparticle mass hierarchies. Thus dark matter experiments along with analyses for the LHC Run-II will provide strong clues to the nature of symmetry breaking at the unification scale.

Phenomenological Implications of Deflected Mirage Mediation: Comparison with Mirage Mediation

We compare the collider phenomenology of mirage mediation and deflected mirage mediation, which are two recently proposed “mixed” supersymmetry breaking scenarios motivated from string compactifications. The scenarios differ in that deflected mirage mediation includes contributions from gauge mediation in addition to the contributions from gravity mediation and anomaly mediation also present in mirage mediation. The threshold effects from gauge mediation can drastically alter the low energy spectrum from that of pure mirage mediation models, resulting in some cases in a squeezed gaugino spectrum and a gluino that is much lighter than other colored superpartners. We provide several benchmark deflected mirage mediation models and construct model lines as a function of the gauge mediation contributions, and discuss their discovery potential at the LHC.

Landscape of supersymmetric particle mass hierarchies in deflected mirage mediation

With the aim of uncovering viable regions of parameter space in deflected mirage mediation (DMM) models of supersymmetry breaking, we study the landscape of particle mass hierarchies for the lightest four non-Standard Model states for DMM models and compare the results to that of minimal supergravity/constrained MSSM (mSUGRA/CMSSM) models, building on previous studies of Feldman, Liu, and Nath. Deflected mirage mediation is a string-motivated scenario in which the soft terms include comparable contributions from gravity mediation, gauge mediation, and anomaly mediation. DMM allows a wide variety of phenomenologically preferred models with light charginos and neutralinos, including novel patterns in which the heavy Higgs particles are lighter than the lightest superpartner. We use this analysis to motivate two DMM benchmark points to be used for more detailed collider studies. One model point has a higgsino-dominated lightest superpartner and a compressed yet heavy spectrum, while the other has a stau NLSP and similar features to mSUGRA/CMSSM models, but with a slightly less stretched spectrum.

Distinguishing LSP archetypes via gluino pair production at LHC13

The search for supersymmetry at Run 1 of LHC has resulted in gluino mass limits m~ & 1:3 TeV for the case where m~ m~ and in models with gaugino mass unication. The increased energy and ultimately luminosity of LHC13 will explore the range m~ g 1:3 2 TeV. We examine how the discovery of SUSY via gluino pair production would unfold via a comparative analysis of three LSP archetype scenarios: 1. mSUGRA/CMSSM model with a bino-like LSP, 2. charged SUSY breaking (CSB) with a wino-like LSP and 3. SUSY with radiatively-driven naturalness (RNS) and a higgsino-like LSP. In all three cases we expect heavy-to-very-heavy squarks as suggested by a decoupling solution to the SUSY

Finitely many Dirac-delta interactions on Riemannian manifolds

This work is intended as an attempt to study the nonperturbative renormalization of bound state problem of finitely many Dirac-delta interactions on Riemannian manifolds, S2, H2, and H3. We formulate the problem in terms of a finite dimensional matrix, called the characteristic matrix Φ. The bound state energies can be found from the characteristic equation Φ(−ν2)A=0. The characteristic matrix can be found after a regularization and renormalization by using a sharp cut-off in the eigenvalue spectrum of the Laplacian, as it is done in the flat space, or using the heat kernel method. These two approaches are equivalent in the case of compact manifolds. The heat kernel method has a general advantage to find lower bounds on the spectrum even for compact manifolds as shown in the case of S2. The heat kernels for H2 and H3 are known explicitly, thus we can calculate the characteristic matrix Φ. Using the result, we give lower bound estimates of the discrete spectrum.

Multidimensional phase space methods for mass measurements and decay topology determination

Collider events with multi-stage cascade decays fill out the kinematically allowed region in phase space with a density that is enhanced at the boundary. The boundary encodes all available information as regards the spectrum and is well populated even with moderate signal statistics due to this enhancement. In previous work, the improvement in the precision of mass measurements for cascade decays with three visible and one invisible particles was demonstrated when the full boundary information is used instead of endpoints of one-dimensional projections. We extend these results to cascade decays with four visible and one invisible particles. We also comment on how the topology of the cascade decay can be determined from the differential distribution of events in these scenarios.