Simplified models for dark matter searches at the LHC

This document outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For -channel, spin-0 and spin-1 mediations are discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented

Simplified models for dark matter searches at the LHC

This document outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For -channel, spin-0 and spin-1 mediations are discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented

Mental health status of healthcare professionals and students of health sciences faculties in Kuwait during the COVID-19 pandemic

Objectives: This study aimed to assess the impact of the COVID-19 pandemic on the mental health status of healthcare professionals (HCPs) and undergraduate students in the health sciences center (HSCUs). In addition, it explored the factors associated with the increased levels of mental health burden among the study population. Methods: A cross-sectional study was performed using two online-administered questionnaires: the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder 7-item (GAD-7), which were distributed in parallel to HCPs and HSCUs in Kuwait. These instruments are validated assessment scales to assess mental health status: depression (PHQ-9) and anxiety (GAD-7). Statistical analyses were carried out using SPSS- version 25. Results: A total of 857 individuals (559 HCPs and 298 HSCUs) participated in this study. The prevalence of moderately severe depression or severe depression (PHQ-9 total score of ≥15) among respondents was 66.6%. The median (interquartile range, IQR) PHQ-9 score was significantly higher among HSCUs (20 {11.5}) compared to HCPs (17 {8}). The prevalence of severe anxiety (GAD-7 total score of ≥15) among respondents was 36.7%. There were no significant differences between the median (IQR) GAD-7 scores among the HCPs (14 {7}) and HSCUs (13 {8}). Binary logistic regression analysis revealed that three variables were significantly and independently associated with severe depression among HCPs. The prevalence of severe depression was found to be greater among females compared to males. In addition, it was significantly lower among those who were aged ≥50 years, and those who reported that they were not in direct contact with COVID-19 patients. Among HSCUs, females showed greater depression than males. In contrast, those aged >29 years and who had no history of chronic disease showed lower depression compared to their counterparts in the 18–29 years age group and who had a chronic disease history. Conclusions: The COVID-19 pandemic had a significant negative impact on the mental health of HCPs and HSCUs in Kuwait. This highlights the need for proactive efforts to support their mental health and well-being through educational campaigns and psychological support programs

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

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

Measurement of the b-hadron production cross section using decays to D*+ μ − X final states in pp collisions at √s = 7 TeV with the ATLAS detector

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at √s = 7 TeV, using 3.3 pb−1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*+μ−X final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT > 9 GeV and |η| < 2.5 is 32.7±0.8(stat.)+4.5−6.8(syst.) μb, higher than the next-to-leadingorder QCD predictions but consistent within the experimental and theoretical uncertainties

Measurement of the production cross section of prompt J/ψ mesons in association with a W ± boson in pp collisions at √s = 7 TeV with the ATLAS detector

The process pp → W ± J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb−1 of s√ = 7 TeV pp collisions at the LHC, the first observation is made of the production of W ± + prompt J/ψ events in hadronic collisions, using W ± → μν μ and J/ψ → μ + μ −. A yield of 27.4+7.5−6.5 W ± + prompt J/ψ events is observed, with a statistical significance of 5.1σ. The production rate as a ratio to the inclusive W ± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated.publishedVersio

Search for heavy lepton resonances decaying to a ZZ boson and a lepton in pppp collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

A search for heavy leptons decaying to a $Z$ boson and an electron or a muon is presented. The search is based on $pp$ collision data taken at $\sqrt{s}=8$ TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$, Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a $Z$ boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded

Search for new phenomena in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in s=\sqrt{s}= 13 pppp collisions with the ATLAS detector

Two searches for new phenomena in final states containing a same-flavour opposite-lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of proton--proton collision data, collected during 2015 and 2016 at a centre-of-mass energy $\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb$^{-1}$, Both searches target the pair production of supersymmetric particles, squarks or gluinos, which decay to final states containing a same-flavour opposite-sign lepton pair via one of two mechanisms: a leptonically decaying Z boson in the final state, leading to a peak in the dilepton invariant-mass distribution around the Z boson mass; and decays of neutralinos (e.g. $\tilde{\chi}_2^0 \rightarrow \ell^+\ell^- \tilde{\chi}_1^0$), yielding a kinematic endpoint in the dilepton invariant-mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.70 TeV (980 GeV).publishedVersio

Search for invisible decays of the Higgs boson produced in association with a hadronically decaying vector boson in pppp collisions at s=8\sqrt{s} = 8 TeV with the ATLAS detector

A search for Higgs boson decays to invisible particles is performed using 20.3 fb\).{-1}\) of $pp$ collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The process considered is Higgs boson production in association with a vector boson $V$ = $W$ or $Z$ that decays hadronically, resulting in events with two or more jets and large missing transverse momentum. No excess of candidates is observed in the data over the background expectation. The results are used to constrain $VH$ production followed by $H$ decaying to invisible particles for the Higgs mass range $115<m_H<300$ GeV. The 95% confidence-level observed upper limit on $\sigma_{VH} \times \text{BR}(H\rightarrow \text{inv.})$ varies from 1.6 pb at 115 GeV to 0.13 pb at 300 GeV. Assuming Standard Model production and including the $gg\rightarrow H$ contribution as signal, the results also lead to an observed upper limit of 78% at 95% confidence level on the branching ratio of Higgs bosons decays to invisible particles at a mass of 125 GeV.publishedVersio

Search for heavy lepton resonances decaying to a ZZ boson and a lepton in pppp collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

A search for heavy leptons decaying to a $Z$ boson and an electron or a muon is presented. The search is based on $pp$ collision data taken at $\sqrt{s}=8$ TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$, Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a $Z$ boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded.publishedVersio