Lepton Jets in (Supersymmetric) Electroweak Processes

We consider some of the recent proposals in which weak-scale dark matter is accompanied by a GeV scale dark sector that could produce spectacular lepton-rich events at the LHC. Since much of the collider phenomenology is only weakly model dependent it is possible to arrive at generic predictions for the discovery potential of future experimental searches. We concentrate on the production of dark states through $Z^0$ bosons and electroweak-inos at the Tevatron or LHC, which are the cleanest channels for probing the dark sector. We properly take into account the effects of dark radiation and dark cascades on the formation of lepton jets. Finally, we present a concrete definition of a lepton jet and suggest several approaches for inclusive experimental searches.Comment: 23 pages, 13 figures, published version, added section 3.3 expanding on lepton jet's morpholog

Superpartner spectrum of minimal gaugino-gauge mediation

We evaluate the sparticle mass spectrum in the minimal four-dimensional construction that interpolates between gaugino and ordinary gauge mediation at the weak scale. We find that even in the hybrid case -- when the messenger scale is comparable to the mass of the additional gauge particles -- both the right-handed as well as the left-handed sleptons are lighter than the bino in the low-scale mediation regime. This implies a chain of lepton production and, consequently, striking signatures that may be probed at the LHC already in the near future.Comment: 8 pages, 3 figures; V2: refs and a few comments added; V3 title change

Discovery Potential for Low-Scale Gauge Mediation at Early LHC

Low-scale gauge-mediated supersymmetry(SUSY)-breaking (GMSB) models with gravitino mass m_{3/2}<16 eV are attractive, since there are no flavor and cosmological problems. In this paper, we thoroughly study the collider signal in the case that the next-to-lightest SUSY particle is the bino or slepton and investigate the discovery potential of the LHC. Our result is applicable to a wider class of GMSB models other than the minimal GMSB models and we pay particular attention to realistic experimental setups. We also apply our analysis to the minimal GMSB models with a metastable SUSY-breaking vacuum and we show, by requiring sufficient stability of the SUSY-breaking vacuum, these models can be tested at an early stage of the LHC.Comment: 21 pages, 7 figures.Texts in section 3.2.2 and 3.2.4 are revised. Captions change

General Neutralino NLSPs at the Early LHC

Gauge mediated supersymmetry breaking (GMSB) is a theoretically well-motivated framework with rich and varied collider phenomenology. In this paper, we study the Tevatron limits and LHC discovery potential for a wide class of GMSB scenarios in which the next-to-lightest superpartner (NLSP) is a promptly-decaying neutralino. These scenarios give rise to signatures involving hard photons, $W$'s, $Z$'s, jets and/or higgses, plus missing energy. In order to characterize these signatures, we define a small number of minimal spectra, in the context of General Gauge Mediation, which are parameterized by the mass of the NLSP and the gluino. Using these minimal spectra, we determine the most promising discovery channels for general neutralino NLSPs. We find that the 2010 dataset can already cover new ground with strong production for all NLSP types. With the upcoming 2011-2012 dataset, we find that the LHC will also have sensitivity to direct electroweak production of neutralino NLSPs.Comment: 26 page

Asymmetric Dark Matter from Leptogenesis

We present a new realization of asymmetric dark matter in which the dark matter and lepton asymmetries are generated simultaneously through two-sector leptogenesis. The right-handed neutrinos couple both to the Standard Model and to a hidden sector where the dark matter resides. This framework explains the lepton asymmetry, dark matter abundance and neutrino masses all at once. In contrast to previous realizations of asymmetric dark matter, the model allows for a wide range of dark matter masses, from keV to 10 TeV. In particular, very light dark matter can be accommodated without violating experimental constraints. We discuss several variants of our model that highlight interesting phenomenological possibilities. In one, late decays repopulate the symmetric dark matter component, providing a new mechanism for generating a large annihilation rate at the present epoch and allowing for mixed warm/cold dark matter. In a second scenario, dark matter mixes with the active neutrinos, thus presenting a distinct method to populate sterile neutrino dark matter through leptogenesis. At late times, oscillations and dark matter decays lead to interesting indirect detection signals.Comment: 32 pages + appendix, references added, minor change

Searches for Long Lived Neutral Particles

An intriguing possibility for TeV scale physics is the existence of neutral long lived particles (LOLIPs) that subsequently decay into SM states. Such particles are many cases indistinguishable from missing transverse energy (MET) at colliders. We propose new methods to search for these particles using neutrino telescopes. We study their detection prospects, assuming production either at the LHC or through dark matter (DM) annihilations in the Sun and the Earth. We find that the sensitivity for LOLIPs produced at the LHC is limited by luminosity and detection energy thresholds. On the other hand, in the case of DM annihilation into LOLIPs, the sensitivity of neutrino telescopes is promising and may extend beyond the reach of upcoming direct detection experiments. In the context of low scale hidden sectors weakly coupled to the SM, such indirect searches allow to probe couplings as small as 10^-15.Comment: 22 pages, 6 figure

Revealing the footprints of squark gluino production through Higgs search experiments at the Large Hadron Collider at 7 TeV and 14 TeV

The invariant mass distribution of the di-photons from the decay of the lighter scalar Higgs boson(h) to be carefully measured by dedicated h search experiments at the LHC may be distorted by the di-photons associated with the squark-gluino events with much larger cross sections in Gauge Mediated Supersymmetry Breaking (GMSB) models. This distortion if observed by the experiments at the Large Hadron Collider at 7 TeV or 14 TeV, would disfavour not only the standard model but various two Higgs doublet models with comparable h - masses and couplings but without a sector consisting of new heavy particles decaying into photons. The minimal GMSB (mGMSB) model constrained by the mass bound on h from LEP and that on the lightest neutralino from the Tevatron, produce negligible effects. But in the currently popular general GMSB(GGMSB) models the tail of the above distribution may show statistically significant excess of events even in the early stages of the LHC experiments with integrated luminosity insufficient for the discovery of h. We illustrate the above points by introducing several benchmark points in various GMSB models - minimal as well as non-minimal. The same conclusion follows from a detailed parameter scan in a simplified GGMSB model recently employed by the CMS collaboration to interpret their searches in the di-photon + \etslash channel. Other observables like the effective mass distribution of the di-photon + X events may also reveal the presence of new heavy particles beyond the Higgs sector. The contamination of the h mass peak and simple remedies are also discussed.Comment: 23 pages, 7 figures, title and organization of the paper is changed, detailed parameter scan in a simplified GGMSB model is added, conclusions and old numerical results remain unchange

Higgs decay with monophoton + MET signature from low scale supersymmetry breaking

We study the decay of a standard model-like Higgs boson into a gravitino and a neutralino, which subsequently decays promptly into another gravitino and a photon. Such a decay can be important in scenarios where the supersymmetry breaking scale is of the order of a few TeV, and in the region of low transverse momenta of the photon, it may provide the dominant contribution to the final state with a photon and two gravitinos. We estimate the relevant standard model backgrounds and the prospects for discovering this Higgs decay through a photon and missing transverse energy signal at the LHC in terms of a simplified model. We also give an explicit model with manifest, but spontaneously broken, supersymmetry in which the usual MSSM soft terms are promoted to supersymmetric operators involving a dynamical goldstino supermultiplet. This model can give rise to a SM-like CP-even neutral Higgs particle with a mass of 125 GeV, without requiring substantial radiative corrections, and with couplings sufficiently large for a signal discovery through the above mentioned Higgs decay channel with the upcoming data from the LHC.Comment: 28 pages, 5 figures, 4 tables; v2: updated to JHEP version, references adde

Pseudomoduli Dark Matter and Quiver Gauge Theories

We investigate supersymmetric models for dark matter which is represented by pseudomoduli in weakly coupled hidden sectors. We propose a scheme to add a dark matter sector to quiver gauge theories with metastable supersymmetry breaking. We discuss the embedding of such scheme in string theory and we describe the dark matter sector in terms of D7 flavour branes. We explore the phenomenology in various regions of the parameters.Comment: 24 pages, 12 figures, JHEP3.cl

Period Increase and Amplitude Distribution of Kink Oscillation of Coronal Loop

Coronal loops exist ubiquitously in the solar atmosphere. These loops puzzle astronomers over half a century. Solar magneto-seismology (SMS) provides a unique way to constrain the physical parameters of coronal loops. Here, we study the evolution of oscillations of a coronal loop observed by the Atmospheric Imaging Assembly (AIA). We measure geometric and physical parameters of the loop oscillations. In particular, we find that the mean period of the oscillations increased from 1048 to 1264 s during three oscillatory cycles. We employ the differential emission measure method and apply the tools of SMS. The evolution of densities inside and outside the loop is analyzed. We found that an increase of density inside the loop and decrease of the magnetic field strength along the loop are the main reasons for the increase in the period during the oscillations. Besides, we also found that the amplitude profile of the loop is different from a profile would it be a homogeneous loop. It is proposed that the distribution of magnetic strength along the loop rather than density stratification is responsible for this deviation. The variation in period and distribution of amplitude provide, in terms of SMS, a new and unprecedented insight into coronal loop diagnostics