Interplay of Direct and Indirect Searches for New Physics

We report recent work on the interplay of collider and flavour physics regarding the search for physics beyond the Standard Model.Comment: 4 pages, based on an invited talk at PANIC11, MIT, Cambridge, USA, 24.-29.7.201

Same-sign top quarks as signature of light stops at the CERN LHC

We present a new method to search for a light scalar top with m_{\tilde{t}_1}\lsim m_t, decaying dominantly into a c-jet and the lightest neutralino, at the LHC. The principal idea is to exploit the Majorana nature of the gluino, leading to same-sign top quarks in events of gluino-pair production followed by gluino decays into top and stop. The resulting signature is 2 b-jets plus 2 same-sign leptons plus additional jets and missing energy. We perform a Monte Carlo simulation for a benchmark scenario, which is in agreement with the recent WMAP bound on the relic density of dark matter, and demonstrate that for m_{\tilde{g}}\lsim 900 GeV and $m_{\tilde{q}}>m_{\tilde{g}}$ the signal can be extracted from the background. Moreover, we discuss the determination of the stop and gluino masses from the shape of invariant-mass distributions. The derivation of the shape formulae is also given.Comment: 20 pages, 6 figures, minor changes; version to appear in PR

Same-sign top quarks as signature of light stops

We present a new method to search for a light scalar top (stop), decaying dominantly into $c\tilde\chi^0_1$, at the LHC. The principal idea is to exploit the Majorana nature of the gluino, leading to same-sign top quarks in events of gluino pair production followed by gluino decays into top and stop. We demonstrate the reach of our method in terms of the gluino mass and the stop-neutralino mass difference.Comment: 4 pages, 1 figure, to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

Status of Higgs couplings after Run-1 of the LHC using Lilith 1.0

We provide an update of the global fits of the couplings of the 125.5 GeV Higgs boson using all publicly available experimental results from Run-1 of the LHC as per Summer 2014. The fits are done by means of the new public code Lilith 1.0. We present a selection of results given in terms of signal strengths, reduced couplings, and for the Two-Higgs-Doublet Models of Type I and II.Comment: 12 pages, 4 figure

Comparison of SUSY mass spectrum calculations

We provide a comparison of the results of four SUSY mass spectrum calculations in mSUGRA: Isajet, SuSpect, SoftSusy, and SPheno. In particular, we focus on the high tan(beta) and focus point regions, where the differences in the results are known to be large.Comment: Contribution to SUSY02, 17-23 Jun 2002, DESY Hamburg, 7 page

Diagnosing Degenerate Higgs Bosons at 125 GeV

We develop diagnostic tools that would provide incontrovertible evidence for the presence of more than one Higgs boson near 125 GeV in the LHC data.Comment: 4 pages, 2 figure

The phenomenological MSSM in view of the 125 GeV Higgs data

The parameter space of the phenomenological MSSM (pMSSM) is explored by means of Markov Chain Monte Charlo (MCMC) methods, taking into account the latest LHC results on the Higgs signal at 125 GeV in addition to relevant low-energy observables and LEP constraints. We use a Bayesian approach to derive posterior densities for the parameters and observables of interests. We find in particular that the Higgs measurements have a significant impact on the parameters mu and tan beta due to radiative corrections to the bottom Yukawa coupling. We show moreover the impact of the most recent dark matter measurements on the probability distributions, and we discuss prospects for the next run of the LHC at 13-14 TeV.Comment: 28 pages, 13 figures; v2: matches version accepted for publication in PR

Thermal leptogenesis and the gravitino problem in the Asaka-Yanagida axion/axino dark matter scenario

A successful implementation of thermal leptogenesis requires the re-heat temperature after inflation T_R to exceed ~2\times 10^9 GeV. Such a high T_R value typically leads to an overproduction of gravitinos in the early universe, which will cause conflicts, mainly with BBN constraints. Asaka and Yanagida (AY) have proposed that these two issues can be reconciled in the context of the Peccei-Quinn augmented MSSM (PQMSSM) if one adopts a mass hierarchy m(sparticle)>m(gravitino)>m(axino), with m(axino) keV. We calculate the relic abundance of mixed axion/axino dark matter in the AY scenario, and investigate under what conditions a value of T_R sufficient for thermal leptogenesis can be generated. A high value of PQ breaking scale f_a is needed to suppress overproduction of axinos, while a small vacuum misalignment angle \theta_i is needed to suppress overproduction of axions. The large value of f_a results in late decaying neutralinos. To avoid BBN constraints, the AY scenario requires a low thermal abundance of neutralinos and high values of neutralino mass. We include entropy production from late decaying saxions, and find the saxion needs to be typically at least several times heavier than the gravitino. A viable AY scenario suggests that LHC should discover a spectrum of SUSY particles consistent with weak scale supergravity; that the apparent neutralino abundance is low; that a possible axion detection signal (probably with m_axion in the sub-micro-eV range) should occur, but no direct or indirect signals for WIMP dark matter should be observed.Comment: 28 pages including 21 .eps figures; high resolution pdf version available at http://www.nhn.ou.edu/~bae

Harmonic drive gear error: Characterization and compensation for precision pointing and tracking

Imperfections and geometry effects in harmonic drive gear reducers cause a cyclic gear error, which at a systems level, results in high frequency torque fluctuations. To address this problem, gear error testing was performed on a wide variety of sizes and types of harmonic drives. It was found that although all harmonic drives exhibit a significant first harmonic, higher harmonics varied greatly with each unit. From life tests, small changes were found in harmonic content, phase shift, and error magnitude (on the order of .008 deg peak-to-peak maximum) occurred for drives with many millions of degrees of output travel. Temperature variations also influenced gear error. Over a spread of approximately 56 C (100 F), the error varied in magnitude approximately 20 percent but changes in a repeatable and predictable manner. Concentricity and parallelness tests of harmonic drive parts resulted in showing alignment influence gear error amplitude. Tests on dedoidaled harmonic drives showed little effect on gear error; surprisingly, in one case for a small drive, gear error actually improved. Electronic compensation of gear error in harmonic drives was shown to be substantially effective for units that are first harmonic dominant

Prospects for Yukawa Unified SO(10) SUSY GUTs at the CERN LHC

The requirement of t-b-\tau Yukawa coupling unification is common in simple grand unified models based on the gauge group SO(10), and it also places a severe constraint on the expected spectrum of superpartners. For Yukawa-unified models with \mu >0, the spectrum is characterized by three mass scales: {\it i}). first and second generation scalars in the multi-TeV range, {\it ii}). third generation scalars, \mu and m_A in the few-TeV range and {\it iii}). gluinos in the \sim 350-500 GeV range with chargino masses around 100-160 GeV. In such a scenario, gluino pair production should occur at large rates at the CERN LHC, followed by gluino three-body decays into neutralinos or charginos. Discovery of Yukawa-unified SUSY at the LHC should hence be possible with only 1 fb^{-1} of integrated luminosity, by tagging multi-jet events with 2--3 isolated leptons, without relying on missing E_T. A characteristic dilepton mass edge should easily be apparent above Standard Model background. Combining dileptons with b-jets, along with the gluino pair production cross section information, should allow for gluino and neutralino mass reconstruction. A secondary corroborative signal should be visible at higher integrated luminosity in the W1Z2-> 3\ell channel, and should exhibit the same dilepton mass edge as in the gluino cascade decay signal.Comment: 25 pages including 18 EPS figure