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.
16726847
Testing neutrino masses in the R-parity violating minimal supersymmetric standard model with LHC results
Within the R–parity violating minimal supersymmetric standard model (MSSM), we use a hierarchical ansatz for the lepton–number violating trilinear Yukawa couplings by relating them to the corresponding Higgs–Yukawa couplings. This ansatz reduces the number of free parameters in the lepton–number violating sector from 36 to 6. Baryon–number violating terms are forbidden by imposing the discrete gauge symmetry Baryon Triality. We fit the lepton–number violating parameters to the most recent neutrino oscillation data, including the mixing angle θ13 found by Daya Bay. We find that we obtain phenomenologically viable neutrino masses and mixings only in the case of normal ordered neutrino masses and that the lepton–number violating sector is unambiguously determined by neutrino oscillation data. We discuss the resulting collider signals for the case of a neutralino as well as a scalar tau lightest supersymmetric particle. We use the ATLAS searches for multi–jet events and large transverse missing momentum in the 0, 1 and 2 lepton channel with 7 TeV center–of–mass energy in order to derive exclusion limits on the parameter space of this R–parity violating supersymmetric model.
45811522
A framework to create customised LHC analyses within CheckMATE
Checkmate  is a framework that allows the user to conveniently test simulated BSM physics events against current LHC data in order to derive exclusion limits. For this purpose, the data runs through a detector simulation and is then processed by a user chosen selection of experimental analyses. These analyses are all defined by signal regions that can be compared to the experimental data with a multitude of statistical tools. 
 
Due to the large and continuously growing number of experimental analyses available, users may quickly find themselves in the situation that the study they are particularly interested in has not (yet) been implemented officially into the Checkmate  framework. However, the code includes a rather simple framework to allow users to add new analyses on their own. This document serves as a guide to this. 
 
In addition, Checkmate  serves as a powerful tool for testing and implementing new search strategies. To aid this process, many tools are included to allow a rapid prototyping of new analyses. 
 
Website: http://checkmate.hepforge.org/ 
Program summary 
Program title: CheckMATE, AnalysisManager 
 
Catalogue identifier: AEUT_v1_1 
 
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEUT_v1_1.html 
 
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland 
 
Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html 
 
No. of lines in distributed program, including test data, etc.: 181436 
 
No. of bytes in distributed program, including test data, etc.: 2169369 
 
Distribution format: tar.gz 
 
Programming language: C++, Python. 
 
Computer: PC, Mac. 
 
Operating system: Linux, Mac OS. 
 
Catalogue identifier of previous version: AEUT_v1_0 
 
Journal reference of previous version: Comput. Phys. Comm. 187(2015)227 
 
Classification: 11.9. 
 
External routines: ROOT, Python, Delphes (included with the distribution) 
 
Does the new version supersede the previous version?: Yes 
 
Nature of problem: The LHC has delivered a wealth of new data that is now being analysed. Both ATLAS and CMS have performed many searches for new physics that theorists are eager to test their model against. However, tuning the detector simulations, understanding the particular analysis details and interpreting the results can be a tedious and repetitive task. Furthermore, new analyses are being constantly published by the experiments and might be not yet included in the official CheckMATE distribution. 
 
Solution method: The AnalysisManager within CheckMATE framework allows the user to easily include new experimental analyses as they are published by the collaborations. Furthermore, completely novel analyses can be designed and added by the user in order to test models at higher centre-of-mass energy and/or luminosity. 
 
Reasons for new version: New features, bug fixes, additional validated analyses. 
 
Summary of revisions: New kinematic variables M_CT, M_T2bl, m_T, alpha_T, razor; internal likelihood calculation; missing energy smearing; efficiency tables; validated tau-tagging; improved AnalysisManager and code structure; new analyses; bug fixes. 
 
Restrictions: Only a subset of available experimental results have been implemented. 
 
Additional comments: Checkmate is built upon the tools and hard work of many people. If Checkmate is used in your publication it is extremely important that all of the following citations are included, 
• 
Delphes 3 [1]. 
 
• 
FastJet [2,3]. 
 
• 
Anti-ktkt jet algorithm [4]. 
 
• 
CLss prescription [5]. 
 
• 
In analyses that use the MT2MT2 kinematical discriminant we use the Oxbridge Kinetics Library [6,7] and the algorithm developed by Cheng and Han [8] which also includes the MT2blMT2bl variable [9]. 
 
• 
In analyses that use the MCTMCT family of kinematical discriminants we use MctLib [10,11] which also includes the MCT⊥MCT⊥ and MCTIIMCTII variables [12]. 
 
• 
All experimental analyses that were used to set limits in the study. 
 
• 
The Monte Carlo event generator that was used. 
 
 
Running time: The running time scales about linearly with the number of input events provided by the user. The detector simulation/analysis of 20000 events needs about 50s/1s for a single core calculation on an Intel Core i5-3470 with 3.2 GHz and 8 GB RAM. 
 
References: 
[1] 
J. de Favereau, C. Delaere, P Demin, A. Giammanco, V. Lematre, et al., “DELPHES 3, A modular framework for fast simulation of a generic collider experiment”, 2013. 
 
[2] 
M. Cacciari, G. P Salam, and G. Soyez, “FastJet User Manual”, Eur. Phys. J., vol. C72, p. 1896, 2012. 
 
[3] 
M. Cacciari and G. P Salam, ”Dispelling the N3 myth for the kt jet-finder”, Phys. Lett., vol. B641, pp. 57–61, 2006. 
 
[4] 
M. Cacciari, G. P Salam, and G. Soyez, “The Anti-k(t) jet clustering algorithm”, JHEP, vol. 0804, p. 063, 2008. 
 
[5] 
A. L. Read, “Presentation of search results: the cl’s technique”, Journal of Physics G: Nuclear and Particle Physics, vol. 28, no. 10, p. 2693, 2002. 
 
[6] 
C. Lester and D. Summers, “Measuring masses of semiinvisibly decaying particles pair produced at hadron colliders”, Phys. Lett., vol. B463, pp. 99–103, 1999. 
 
[7] 
A. Barr, C. Lester, and P Stephens, “m(T2): The Truth behind the glamour”, J. Phys., vol. G29, pp. 2343–2363, 2003. 
 
[8] 
H.-C. Cheng and Z. Han, “Minimal Kinematic Constraints and m(T2)”, JHEP, vol. 0812, p. 063, 2008. 
 
[9] 
Y. Bai, H.-C. Cheng, J. Gallicchio, and J. Gu, “Stop the Top Background of the Stop Search”, JHEP, vol. 1207, p. 110, 2012. 
 
[10] 
D. R. Tovey, “On measuring the masses of pair-produced semi-invisibly decaying particles at hadron colliders”, JHEP, vol. 0804, p. 034, 2008. 
 
[11] 
G. Polesello and D. R. Tovey, “Supersymmetric particle mass measurement with the boost-corrected contransverse mass”, JHEP, vol. 1003, p. 030, 2010. 
 
[12] 
K. T. Matchev and M. Park, “A General method for determining the masses of semi-invisibly decaying particles at hadron colliders”, Phys. Rev. Lett., vol. 107, p. 061801, 2011.
118704767
First LHC Constraints on Neutralinos
Abstract The ATLAS and CMS Collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs-like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that most of the region μ 170 GeV , M 1 70 GeV at tan β ∼ 10 and μ 120 GeV , M 1 70 GeV at tan β ∼ 40 is disfavored.
53580211
The higgsino–singlino world at the large hadron collider
We consider light higgsinos and singlinos in the next-to-minimal supersymmetric standard model at the large hadron collider. We assume that the singlino is the lightest supersymmetric particle and that the higgsino is the next-to-lightest supersymmetric particle with the remaining supersymmetric particles in the multi-TeV range. This scenario, which is motivated by the flavor and CP issues, provides a phenomenologically viable dark matter candidate and improved electroweak fit consistent with the measured Higgs mass. Here, the higgsinos decay into on (off)-shell gauge boson and the singlino. We consider the leptonic decay modes and the resulting signature is three isolated leptons and missing transverse energy which is known as the trilepton signal. We simulate the signal and the Standard Model backgrounds and present the exclusion region in the higgsino–singlino mass plane at the large hadron collider at $$\sqrt{s}=14$$s=14 TeV for an integrated luminosity of 300 fb$$^{-1}$$-1.
119300805
Light stop phenomenology
We consider the discovery potential of light stops in the MSSM at the LHC. Here, we assume that the lightest neutralino is the LSP and that the lighter stop i s the NLSP. Direct stop pair production is difficult to probe in scenarios with a small mass splitting between the stop and a neutralino. We discuss two different search channels: the monojet and the two b‐flavoured jets and large missing transverse energy signature. We present the discovery reach in the stop‐neutralino mass plane for both channels. The latter process is sensitive to the stop‐h iggsino‐b quark coupling. This allows us to test a supersymmetry relation involving superpotential couplings. We briefly comment on the possible precision with which the coupling can be measured.
120800011
A common scale for the invisible axion, local SUSY GUTs and Saxino decay
Abstract We identify the scale 10 11–12 GeV as that of the invisible axion and the SUSY breaking scale of local SUSY GUTs. The saxino ( a SUSY partner of the axino; the other partner is the invisble axion) decay is also commented on.
119181982
Decaying dark matter with heavy axino
Just one decaying dark matter chiral multiplet N is introduced at the TeV scale beyond the minimal supersymmetric standard model. A heavy axino needed for the strong CP solution, decaying to N and minimal supersymmetric standard model particles, enables us to calculate its abundance in the scenario that the heavy axino, once dominating the energy density of the Universe, decays after the lightest supersymmetric particle decouples. Dimension 6 interactions arising from the mass scale of E{sup {+-}} allow the lifetime of the fermionic or the bosonic superpartner of N in the 10{sup 27} s range to be compatible with the recent astrophysical bounds. A diagrammatic strategy obtaining a suppression factor 1/M{sup 2} is also given.
118530966
How accurately can we measure the hydrogen 2S->1S transition rate from the cosmological data?
Recent progress in observational cosmology, and especially the forthcoming PLANCK mission data, open new directions in so-called precision cosmology. In this paper we illustrate this statement considering the accuracy of cosmological determination of the two-quanta decay rate of 2s hydrogen atom state. We show that the PLANCK data will allow us to measure this decay rate significantly better than in the laboratory experiments.
54964474
Self-tuning of the cosmological constant
Here, I discuss the cosmological constant problems, in particular paying attention to the vanishing cosmological constant. There are three cosmological constant problems in particle physics. Hawking's idea of calculating the probability amplitude for our Universe is peaked at = 0 which I try to obtain after the initial inflationary period using a self-tuning model. I review what has been discussed on the Hawking type calculation with H2 Lagrangian, and present a (probably) correct way to calculate the amplitude, and show that the Kim-Kyae-Lee self-tuning model allows a finite range of parameters for the = 0 to have a singularly large probability, approached from the AdS side.
14529222
Higgsino mass matrix ansatz for MSSM
Abstract An ansatz, Det M H =0, for the Higgsino mass matrix is suggested toward the minimal supersymmetric standard model (MSSM). Small instanton solutions effective around the GUT scale can fulfill this condition. An argument that the couplings contain a moduli field is given for a dynamical realization of this Higgsino mass matrix ansatz. We also present a string orbifold trinification toward this realization.