125375882
A REVIEW OF SPIN DETERMINATION AT THE LHC
We review the prospects of direct spin determination of new particles which may be discovered at the LHC. We discuss the general framework and the different channels which contain spin information. The experimental challenges associated with such measurements are briefly discussed and the most urgent unresolved problems are emphasized.
2358256
Non-abelian dark sectors and their collider signatures
Motivated by the recent proliferation of observed astrophysical anomalies, Arkani-Hamed et al. have proposed a model in which dark matter is charged under a non-abelian ``dark'' gauge symmetry that is broken at ~1 GeV. In this paper, we present a survey of concrete models realizing such a scenario, followed by a largely model-independent study of collider phenomenology relevant to the Tevatron and the LHC. We address some model building issues that are easily surmounted to accommodate the astrophysics. While SUSY is not necessary, we argue that it is theoretically well-motivated because the GeV scale is automatically generated. Specifically, we propose a novel mechanism by which mixed D-terms in the dark sector induce either SUSY breaking or a super-Higgs mechanism precisely at a GeV. Furthermore, we elaborate on the original proposal of Arkani-Hamed et al. in which the dark matter acts as a messenger of gauge mediation to the dark sector. In our collider analysis we present cross-sections for dominant production channels and lifetime estimates for primary decay modes. We find that dark gauge bosons can be produced at the Tevatron and the LHC, either through a process analogous to prompt photon production or through a rare Z decay channel. Dark gauge bosons will decay back to the SM via ``lepton jets'' which typically contain >2 and as many as 8 leptons, significantly improving their discovery potential. Since SUSY decays from the MSSM will eventually cascade down to these lepton jets, the discovery potential for direct electroweak-ino production may also be improved. Exploiting the unique kinematics, we find that it is possible to reconstruct the mass of the MSSM LSP. We also present several non-SUSY and SUSY decay channels that have displaced vertices and lead to multiple leptons with partially correlated impact parameters.
18862053
A REVIEW OF SPIN DETERMINATION AT THE LHC
Spin measurement is crucial in distinguishing major scenarios of TeV scale new physics once it is discovered at the Large Hadron Collider (LHC). We give a brief survey of methods of measuring the spin of new physics particles at the LHC. We focus on the case in which a long lived massive neutral particle is produced at the end of every cascade decay and escape detection. This is the case for R-parity preserving supersymmetry, Little Higgs models with T-parity, extra-dimensional models with KK-parity, and a large class of similar models and scenarios. After briefly commenting on measuring spin by combining mass and rate information, we concentrate on direct measurement by observing angular correlations among decay products of the new physics particles. We survey a wide range of possible channels, discuss the construction of possible correlation variables, and outline experimental challenges. We also briefly survey the Monte Carlo tools which are useful in studying such correlations.
53402999
Terrestrial and Solar Limits on Long-Lived Particles in a Dark Sector
Dark matter charged under a new gauge sector, as motivated by recent data, suggests a rich GeV-scale ``dark sector'' weakly coupled to the standard model by gauge kinetic mixing. The new gauge bosons can decay to standard model leptons, but this mode is suppressed if decays into lighter ``dark sector'' particles are kinematically allowed. These particles in turn typically have macroscopic decay lifetimes that are constrained by two classes of experiments, which we discuss. Lifetimes of $10\text{ }\text{ }\mathrm{cm}\ensuremath{\lesssim}c\ensuremath{\tau}\ensuremath{\lesssim}{10}^{8}\text{ }\text{ }\mathrm{cm}$ are constrained by existing terrestrial beam-dump experiments. If, in addition, dark matter captured in the Sun (or Earth) annihilates into these particles, lifetimes up to $\ensuremath{\sim}{10}^{15}\text{ }\text{ }\mathrm{cm}$ are constrained by solar observations. These bounds span 14 orders of magnitude in lifetime, but they are not exhaustive. Accordingly, we identify promising new directions for experiments including searches for displaced di-muons in $B$ factories, studies at high-energy and -intensity proton beam dumps, precision gamma-ray and electronic measurements of the Sun, and milli-charge searches reanalyzed in this new context.
119203743
RECAST — extending the impact of existing analyses
Searches for new physics by experimental collaborations represent a significant investment in time and resources. Often these searches are sensitive to a broader class of models than they were originally designed to test. We aim to extend the impact of existing searches through a technique we call recasting. A framework designed to facilitate the usage of this technique, called RECAST, is presented. We illustrate the issues and subtleties involved through several examples, including new results obtained from the reanalysis of archived LEP data. Website:www.recast.it
16158887
The littlest Higgs in anti-de Sitter space
We implement the SU(5)/SO(5) littlest Higgs theory in a slice of 5D Anti-de Sitter space bounded by a UV brane and an IR brane. In this model, there is a bulk SU(5) gauge symmetry that is broken to SO(5) on the IR brane, and the Higgs boson is contained in the Goldstones from this breaking. All of the interactions on the IR brane preserve the global symmetries that protect the Higgs mass, but a radiative potential is generated through loops that stretch to the UV brane where there are explicit SU(5) violating boundary conditions. Like the original littlest Higgs, this model exhibits collective breaking in that two interactions must be turned on in order to generate a Higgs potential. In AdS space, however, collective breaking does not appear in coupling constants directly but rather in the choice of UV brane boundary conditions. We match this AdS construction to the known low energy structure of the littlest Higgs and comment on some of the tensions inherent in the AdS construction. We calculate the 5D Coleman-Weinberg effective potential for the Higgs and find that collective breaking is manifest. In a simplified model with only the SU(2) gauge structure and the top quark, the physical Higgs mass can be of order 200 GeV with no considerable fine tuning (25%). We sketch a more realistic model involving the entire gauge and fermion structure that also implements T-parity, and we comment on the tension between T-parity and flavor structure.
121839880
The influence of the nuclear medium on K+ total cross sections
Abstract The study of the K + total cross sections on a wide range of nuclei has revealed important modifications of the free-space K + -nucleon interaction when the nucleon is embedded in a nucleus. Data indicating such an effect were first obtained in a comparison of the total cross sections on carbon and deuterium. In this letter we report new measurements on 6 Li, silicon, and calcium, and demonstrate that the previously reported modifications occur quite generally.