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.
16537102
On the existence of angular correlations in decays with heavy matter partners
If heavy partners of the Standard Model matter fields are discovered at the LHC it will be imperative to determine their spin in order to uncover the underlying theory. In decay chains, both the spin and the mass hierarchy of all particles involved can influence the resulting angular correlations. We present the necessary conditions for decays involving the matter partners to exhibit angular correlations. In particular we find that when the masses are not degenerate, a heavy fermionic sector always displays angular correlations in cascade decays. When the masses are closely degenerate the size of spin effects is controlled by a global phase parameter. In a large region of the parameter space, correlations are strongly suppressed. In other regions, such as in UED model where this phase is fixed by 5-d Lorentz invariance, the correlations are pronounced. In addition, we show that in certain cases one may even have enough information to determine the spin of other heavy partners involved in the decay (such as the Lightest Stable Partner or a heavy gluon).
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
14441164
Capture of Inelastic Dark Matter in the Sun
We consider the capture of dark matter in the Sun by inelastic scattering against nuclei as in the inelastic dark matter scenario. We show that, assuming a WIMP-nucleon cross-section of σn = 10−40 cm2 the resulting capture rate and density are sufficiently high so that current bounds on the muon neutrino flux from the Sun rule out any appreciable annihilation branching ratio of WIMPs into W+W−, Z0Z0, τ+τ−, t and neutrinos. Slightly weaker bounds are also available for annihilations into b and c. Annihilations into lighter particles that may produce neutrinos, such as μ+μ−, pions and kaons are unconstrained since those stop in the Sun before decaying. Interestingly enough, this is consistent with some recent proposals motivated by the PAMELA results for the annihilation of WIMPs into light bosons which subsequently decay predominantly into light leptons and pions.
123311038
A fifth force and the mediation of supersymmetry breaking
In this talk I will discuss a new mechanism for the mediation of supersymmetry breaking [1]. It relies on the existence of a fifth force, or what is more often refer to as a Z′ gauge‐boson. The existence of supersymmetry and an extra gauge‐boson is well motivated by the type of high‐energy theories (GUT models and string constructions) considered in the literature. The fact that neither has yet been seen is a possible hint that the two are linked and the present work is an attempt at exploring this connection.
15065831
Spin measurements in cascade decays at the LHC
We systematically study the possibility of determining the spin of new particles after their discovery at the LHC. We concentrate on angular correlations in cascade decays. Motivated by constraints of electroweak precision tests and the potential of providing a Cold Dark Matter candidate, we focus on scenarios of new physics in which some discrete symmetry guarantees the existence of stable neutral particles which escape the detector. More specifically, we compare supersymmetry with another generic scenario in which new physics particles have the same spin as their Standard Model partners. A survey of possibilities of observing spin correlations in a broad range of decay channels is carried out, with interesting ones identified. Rather than confining ourselves to one ``collider friendly benchmark point (such as SPS1a), we describe the parameter region in which any particular decay channel is effective. We conduct a more detailed study of chargino's spin determination in the decay channel → q + ± → q + W± + LSP. A scan over the chargino and neutralino masses is performed. We find that as long as the spectrum is not too degenerate the prospects for spin determination in this channel are rather good.
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.