Phenomenology of Universal Extra Dimensions

In this proceeding, the phenomenology of Universal Extra Dimensions (UED), in which all the Standard Model fields propagate, is explored. We focus on models with one universal extra dimension, compactified on an $S_1/Z_2$ orbifold. We revisit calculations of Kaluza-Klein (KK) dark matter without an assumption of the KK mass degeneracy including all possible coannihilations. We then contrast the experimental signatures of low energy supersymmetry and UED.Comment: 4 pages, 6 figures, 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

Dark Matter Particle Spectroscopy at the LHC: Generalizing MT2 to Asymmetric Event Topologies

We consider SUSY-like missing energy events at hadron colliders and critically examine the common assumption that the missing energy is the result of two identical missing particles. In order to experimentally test this hypothesis, we generalize the subsystem MT2 variable to the case of asymmetric event topologies, where the two SUSY decay chains terminate in different "children" particles. In this more general approach, the endpoint MT2max of the MT2 distribution now gives the mass Mp(Mc(a),Mc(b)) of the parent particle as a function of two input children masses Mc(a) and Mc(b). We propose two methods for an independent determination of the individual children masses Mc(a) and Mc(b). First, in the presence of upstream transverse momentum P(UTM) the corresponding function Mp(Mc(a),Mc(b),P(UTM)) is independent of P(UTM) at precisely the right values of the children masses. Second, the previously discussed MT2 "kink" is now generalized to a "ridge" on the 2-dimensional surface Mp(Mc(a),Mc(b)). As we show in several examples, quite often there is a special point along that ridge which marks the true values of the children masses. Our results allow collider experiments to probe a multi-component dark matter sector directly and without any theoretical prejudice.Comment: 50 pages, 31 figures, includes a new Appendix, references added, typos correcte

Superpartner mass measurements with 1D decomposed MT2

We propose a new model-independent technique for mass measurements in missing energy events at hadron colliders. We illustrate our method with the most challenging case of a short, single-step decay chain. We consider inclusive same-sign chargino pair production in supersymmetry, followed by leptonic decays to sneutrinos. We introduce two one-dimensional decompositions of the Cambridge MT2 variable: MT2_\parallel and MT2_\perp, on the direction of the upstream transverse momentum PT and the direction orthogonal to it, respectively. We show that the sneutrino mass can be measured directly by minimizing the number of events N in which MT2 exceeds a certain threshold, conveniently measured from the endpoint MT2^max_\perp.Comment: 5 pages, 3 figures. Revised version, one new figure, results now include detector simulation, conclusions unchange

A General Method for Model-Independent Measurements of Particle Spins, Couplings and Mixing Angles in Cascade Decays with Missing Energy at Hadron Colliders

We outline a general strategy for measuring spins, couplings and mixing angles in the case of a heavy partner decay chain terminating in an invisible particle. We consider the common example of a new scalar or fermion D decaying sequentially to other new particles C, B and A by emitting a quark jet j and two leptons ln and lf. We derive analytic formulas for the dilepton {ln,lf} and the two jet-lepton ({j,ln} and {j,lf}) invariant mass distributions for most general couplings and mixing angles of the new partners. We then consider various spin assignments for the particles A, B, C and D, and derive the relevant functional basis for the invariant mass distributions which contains the intrinsic spin information and does not depend on the couplings and mixing angles. We propose a new method for determining the spins of the new partners, using the three experimentally observable distributions {l+,l-}, {j,l+}+{j,l-} and {j,l+}-{j,l-}. We show that the former two only depend on a single model-dependent parameter alpha, while the latter may depend on two other parameters beta and gamma. By fitting these distributions to our set of basis functions, we are able to do a pure measurement of the spins per se. Our method is also applicable at a pp-bar collider such as the Tevatron, for which the previously proposed lepton charge asymmetry is identically zero and does not contain any spin information. In the process of determining the spins, we also obtain an independent measurement of the parameters alpha, beta and gamma, which represent certain combinations of the couplings and the mixing angles of the heavy partners A, B, C and D.Comment: 67 pages, 29 figures, typeset in JHEP styl

Supersolid phase in spin dimer XXZ systems under magnetic field

Using quantum Monte Carlo method, we study, under external magnetic fields, the ground state phase diagram of the two-dimensional spin $S$=1/2 dimer model with an anisotropic intra-plane antiferromagnetic coupling. With the anisotropy $4 \gtrsim \Delta \gtrsim 3$, a supersolid phase characterized by a non-uniform bose condensate density that breaks translational symmetry is found. The rich phase diagram also contains a checkerboard solid and two different types of superfluid phase formed by $S_z=+1$ and $S_z=0$ spin triplets, with finite staggered magnetization in z-axis and in-plane direction, respectively. As we show, the model can be realized as a consequence of including the next nearest neighbor coupling among dimers and our results suggest that spin dimer systems may be an ideal model system to study the supersolid phase.Comment: 4 pages, 5 figure

Validation of multiprocessor systems

Experiments that can be used to validate fault free performance of multiprocessor systems in aerospace systems integrating flight controls and avionics are discussed. Engineering prototypes for two fault tolerant multiprocessors are tested

Money, desire and citizenship: negotiating urban citizenship among rural-to-urban migrant male sex workers in China

Session on Migrant Sex Workers and Trafficked Persons into Forced Prostitution: Unique Challenges Facing Diverse PopulationsAs part of a massive rural-to-urban migrant population of more than 100 million in contemporary China, rural male migrants in their early twenties are increasingly joining the sex industry, offering sexual services to other men. This paper seeks to understand how these male sex workers (in the local parlance, ''money boys'') suffer from multiple levels of discrimination and stigmatization both from society at large and the gay community in particular. In-depth semi-structured face-to-face interviews were conducted in Beijing and Shanghai, China. Informants were recruited through referral from an NGO with a strong men who have sex with men (MSM) network, and using snowball technique. Between 2004 and 2005, thirty ''money boys'' were interviewed (Beijing, n514; Shanghai, n516). Respondents were mainly single, young, homo-sexual, rural migrants with a secondary education. They employed various strategies - conforming, performing, rejecting, escaping - in handling three major interlocking stigmatized identities: rural migrants, sex workers and MSM. They struggle under a ''hierarchy of citizenship'' along the lines of class, work, gender, sexuality, origin of birth, etc., in order to survive. By viewing their coping strategies as a citizenship-making process, this paper argues that they negotiate a notion of identity under the confines of the dominant ideal of urban citizenship. This paper thus contributes to recent debates on citizenship by enhancing our understanding of a neglected group in cities, whose marginality does not fit within the dominant ideal of (urban) citizenship.postprintThe 7th Conference of the International Association for the Study of Sexuality, Culture and Society (IASSCS 2009), Hanoi, Vietnam, 15-18 April 2009