82 research outputs found

    Simplified Models for Dark Matter and Missing Energy Searches at the LHC

    Get PDF
    The study of collision events with missing energy as searches for the dark matter (DM) component of the Universe are an essential part of the extensive program looking for new physics at the LHC. Given the unknown nature of DM, the interpretation of such searches should be made broad and inclusive. This report reviews the usage of simplified models in the interpretation of missing energy searches. We begin with a brief discussion of the utility and limitation of the effective field theory approach to this problem. The bulk of the report is then devoted to several different simplified models and their signatures, including s-channel and t-channel processes. A common feature of simplified models for DM is the presence of additional particles that mediate the interactions between the Standard Model and the particle that makes up DM. We consider these in detail and emphasize the importance of their inclusion as final states in any coherent interpretation. We also review some of the experimental progress in the field, new signatures, and other aspects of the searches themselves. We conclude with comments and recommendations regarding the use of simplified models in Run-II of the LHC.Comment: v2. references added, version submitted to journal. v1. 47 pages, 13 plot

    Quasi-elastic polarization-transfer measurements on the deuteron in anti-parallel kinematics

    Full text link
    We present measurements of the polarization-transfer components in the 2^2H(e,ep)(\vec e,e'\vec p) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, pmissp_{\rm miss}, up to 220 MeV/c/c, and Q2=0.65Q^2=0.65 (GeV/c)2({\rm GeV}/c)^2. These measurements, performed at the Mainz Microtron (MAMI), were motivated by theoretical calculations which predict small final-state interaction (FSI) effects in these kinematics, making them favorable for searching for medium modifications of bound nucleons in nuclei. We find in this kinematic region that the measured polarization-transfer components PxP_x and PzP_z and their ratio agree with the theoretical calculations, which use free-proton form factors. Using this, we establish upper limits on possible medium effects that modify the bound proton's form factor ratio GE/GMG_E/G_M at the level of a few percent. We also compare the measured polarization-transfer components and their ratio for 2^2H to those of a free (moving) proton. We find that the universal behavior of 2^2H, 4^4He and 12^{12}C in the double ratio (Px/Pz)A(Px/Pz)1H\frac{(P_x/P_z)^A}{(P_x/P_z)^{^1\rm H}} is maintained in the positive missing-momentum region

    Case report: Anorexia nervosa and unspecified restricting-type eating disorder in Jewish ultra-orthodox religious males, leading to severe physical and psychological morbidity

    Get PDF
    BackgroundYoung Jewish Ultra-Orthodox women usually show less disturbances in body image and eating in comparison to less religious communities. By contrast, problems with eating are highly unknown and unrecognized in Jewish Ultra-Orthodox males.AimTo investigate whether in Ultra-Orthodox males, restricting-type AN (AN-R) with highly obsessional physical activity and unspecified restricting eating disorder (ED) in the context of obsessive–compulsive disorder (OCD) would lead to severe physical and emotional morbidity.ResultsThe study included two groups: the first, 3 adolescents with AN-R developing severely increased ritualized obsessional physical activity in addition to restricting eating, requiring inpatient treatment because of severe bradycardia. These youngsters ignored the severity of their obsessional physical activity, continuing with it in hospital despite their grave medical condition. One student began extensive training for triathlon, whereas another student, upon remitting from AN, developed severe muscle dysmorphia. These findings suggest that young Ultra-Orthodox males with AN may develop obsessional physical activity to increase their muscle mass rather than to lose weight Another four Jewish Ultra-Orthodox males developed malnutrition in the context of severe OCD, with no evidence of dieting or body-image disturbances. These individuals developed highly obsessional adherence to different Jewish religious rules, including prolonged praying, asceticism, and overvalued strict adherence to Jewish Kashrut rules of eating, leading in all cases to severe food restriction. They were highly unaware of their severe weight loss and required hospitalization because of severe physical disturbances associated with malnutrition. Moreover, most did not cooperate with their treatment, and their ED-related obsessionality was mostly resistant to psychopharmacotherapy.ConclusionOwing to their highly ritualistic rigid way of life, combined with the need for excellency in studying, Jewish Ultra-Orthodox adolescent males with AN might be at a specific risk of developing severe physical disturbances if their illness is associated with highly perfectionistic obsessional physical activity. Second, Jewish Ultra-Orthodox religious males with OCD might be at a specific risk for severe undernutrition, as their rigid relentless observance of Jewish everyday laws might highly interfere with their eating

    Recent highlights from GENIE v3

    Get PDF
    Funder: u.s. department of energy; doi: http://dx.doi.org/10.13039/100000015AbstractThe release of GENIE v3.0.0 was a major milestone in the long history of the GENIE project, delivering several alternative comprehensive neutrino interaction models, improved charged-lepton scattering simulations, a range of beyond the Standard Model simulation capabilities, improved experimental interfaces, expanded core framework capabilities, and advanced new frameworks for the global analysis of neutrino scattering data and tuning of neutrino interaction models. Steady progress continued following the release of GENIE v3.0.0. New tools and a large number of new physics models, comprehensive model configurations, and tunes have been made publicly available and planned for release in v3.2.0. This article highlights some of the most recent technical and physics developments in the GENIE v3 series.</jats:p

    Study of ordered hadron chains with the ATLAS detector

    Get PDF
    La lista completa de autores que integran el documento puede consultarse en el archivo

    A search for resonances decaying into a Higgs boson and a new particle X in the XH→qqbb final state with the ATLAS detector

    Get PDF
    A search for heavy resonances decaying into a Higgs boson (HH) and a new particle (XX) is reported, utilizing 36.1 fb1^{-1} of proton-proton collision data at s=\sqrt{s} = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle XX is assumed to decay to a pair of light quarks, and the fully hadronic final state XHqqˉbbˉXH \rightarrow q\bar q'b\bar b is analysed. The search considers the regime of high XHXH resonance masses, where the XX and HH bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XHXH mass versus XX mass is scanned for evidence of a signal, over a range of XHXH resonance mass values between 1 TeV and 4 TeV, and for XX particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XHXH and XX masses, on the production cross-section of the XHqqˉbbˉXH\rightarrow q\bar q'b\bar b resonance

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

    Get PDF
    A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

    Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.