46481679
An adjustable Cosmological Constant
Jihn E. Kim Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea DOI: http://dx.doi.org/10.3204/DESY-PROC-2010-03/kim jihn After showing the axion couplings, I review the Hawking type solution of the cosmological constant problem, present a (probably) correct way to calculate the probability amplitude, and show that the Kim-Kyae-Lee self-tuning model allows a finite range of parameters for the Λ = 0 to have a singularly large probability, approached from the AdS side.
119316975
GMSB at a stable vacuum and MSSM without exotics from heterotic string
Abstract We show that it is possible to introduce the confining hidden sector gauge group SU ( 5 ) ′ with the chiral matter 10 0 ′ plus 5 ¯ 0 ′ , which are neutral under the standard model gauge group, toward a gauge mediated supersymmetry breaking (GMSB) in a Z 12 − I orbifold compactification of E 8 × E 8 ′ heterotic string. Three families of MSSM result without exotics. We also find a desirable matter parity P (or R-parity) assignment. We note that this model contains the spectrum of the Lee–Weinberg model which has a nice solution of the μ problem.
18138135
Neutrino masses from discrete gauge symmetries
Abstract We investigate a model with an extra Z 2 gauge symmetry in the Standard Model. The symmetry gives a structure to the mass matrix for the neutrinos. With two extra Higgs singlets and two extra singlet right-handed neutrinos we can build a model that fits the requirements of the MSW solution of the Solar neutrino problem. With a third singlet right-handed neutrino it is also possible to have a 10 eV neutrino.
119883211
Conflicts between B-violating phenomena in supergravity models
Abstract We show that there is an incompatibility between matter stability and cosmological baryon production in standard N = 1 supergravity models. This discrepancy emerges from the bound on the reheating temperature T rh ⩽ 10 10 GeV which comes from the restriction on the gravitino decay after inflation. Some weird possibilities to bypass the controversy are also analyzed.
15739165
SO(10)-like Superstring Standard Model with R-parity from the Heterotic String
We construct a supersymmetric standard model in the context of the Z_{12-I} orbifold compactification of the E_8 x E_8' heterotic string theory. The gauge group is SU(3)_c x SU(2)_L x U(1)_Y x U(1)^4 x [SO(10) x U(1)^3]' with sin^2\theta_W = 3/8. We obtain three families of SO(10) spinor-like chiral matter states, and Higgs doublets. All other extra states are exactly vector-like under the standard model gauge symmetry. There are numerous standard model singlets, many of which get VEVs such that only the standard model gauge symmetry survives and desired Yukawa couplings can be generated at lower energies. In particular, all vector-like exotic states achieve superheavy masses and the R-parity can be preserved.
14574575
Effective Gauss-Bonnet interaction in Randall-Sundrum compactification
The effective gravitational interaction below the Planck scale in the Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we find that there exists another static solution with a positive bulk cosmological constant. Also, there exist solutions for a positive visible sector cosmological constant, which is needed for a later Friedmann-Robertson-Walker universe.
14834509
Electroweak Contributions to Squark Pair Production
We compute electroweak contributions to the production of squark pairs at hadron colliders. These include the exchange of electroweak gauge bosons in the $s-$channel as well as electroweak gaugino exchange in the $t-$ and/or $u-$channel. In many cases these can interfere with the dominant QCD contributions. As a result, we find sizable contributions to the production of two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary between -40 and $+55%$, depending on size and sign of the SU(2) gaugino mass. The electroweak contribution to the total squark pair production rate at the LHC is about 3.5 times smaller.
119218380
Collider signatures of minimal flavor mixing from stop decay length measurements
We investigate the prospects to extract supersymmetric couplings from a decay length measurement at the LHC. Specifically, we exploit the opportunity of a light and long-lived stop which is pair-produced through gluinos in association with like-sign top quarks. Any observed finite value of the stop decay length strongly supports models in which flavor is broken in a minimal way solely by the standard model Yukawa couplings. We find that a 1 picosecond stop lifetime, dominated by t-tilde{yields}c{chi}{sup 0} decays, yields macroscopic transverse impact parameters of about 180 microns. If the lightest neutralino is predominantly Higgsino or very close in mass to the light stop, the stop lifetime even increases and allows to observe stop tracks and possibly secondary vertices directly. Measuring squark flavor violation with the stop decay length works also with a gravitino lightest supersymmetric particle if the neutralino is the next lightest supersymmetric particle. For this case, opportunities from t-tilde{yields}c{chi}{sup 0}{yields}c{gamma}G-tilde decays for very light gravitinos with mass < or approx. keV are pointed out.
54573705
Constraints on the $R$-parity violating minimal supersymmetric standard model with neutrino masses from multilepton studies at the LHC
In a recent paper, we proposed a hierarchical ansatz for the lepton-number-violating trilinear Yukawa couplings of the R-parity violating minimal supersymmetric standard model. As a result, the number of free parameters in the lepton-number-violating sector was reduced from 36 to 6. Neutrino oscillation data fixes these six parameters, which also uniquely determines the decay modes of the lightest supersymmetric particle and thus governs the collider signature at the LHC. A typical signature of our model consists of multiple leptons in the final state and significantly reduced missing transverse momentum compared to models with R-parity conservation. In this work, we present exclusion limits on our model based on multilepton searches performed at the Large Hadron Collider with 7 TeV center-of-mass energy in 2011 while accommodating a 125 GeV Higgs.
119259465
‘Stop’ that ambulance! New physics at the LHC?
A bstractA number of LHC searches now display intriguing excesses. Most prominently, the measurement of the W+W− cross-section has been consistently ∼ 20% higher than the theoretical prediction across both ATLAS and CMS for both 7 and 8 TeV runs. More recently, supersymmetric searches for final states containing two or three leptons have also seen more events than predicted in certain signal regions. We show that a supersymmetric model containing a light stop, winos and binos can consistently match the data. We perform a fit to all measurements and searches that may be sensitive to our model and find a reduction in the log-likelihood of 15.4 compared to the Standard Model which corresponds to 3.5-σ once the extra degrees of freedom in the fit are considered.
122236431
A telescope for observation from space of extreme lightnings in the upper atmosphere
A new type of telescope with a wide field-of-view and functions of fast zoom-in has been introduced. Two kinds of MEMS (Micro-Electro-Mechanical Systems) micromirrors, digital and analog, are used for reflectors of the telescope, placed at different focal lengths. We apply this technology to the observation from space of TLE (Transient Luminous Events), extremely large transient sparks occurring at the upper atmosphere. TLE are one type of important backgrounds to be understood for future space observation of UHECR (Ultra-High Energy Cosmic Rays). The launch of the payload carried by a Russian microsatellite is foreseen in the middle of 2008.