LHC Phenomenology of an Extended Standard Model with a Real Scalar Singlet

Gauge singlet extensions of the Standard Model (SM) scalar sector may help remedy its theoretical and phenomenological shortcomings while solving outstanding problems in cosmology. Depending on the symmetries of the scalar potential, such extensions may provide a viable candidate for the observed relic density of cold dark matter or a strong first order electroweak phase transition needed for electroweak baryogenesis. Using the simplest extension of the SM scalar sector with one real singlet field, we analyze the generic implications of a singlet-extended scalar sector for Higgs boson phenomenology at the Large Hadron Collider (LHC). We consider two broad scenarios: one in which the neutral SM Higgs and singlet mix and the other in which no mixing occurs and the singlet can be a dark matter particle. For the first scenario, we analyze constraints from electroweak precision observables and their implications for LHC Higgs phenomenology. For models in which the singlet is stable, we determine the conditions under which it can yield the observed relic density, compute the cross sections for direct detection in recoil experiments, and discuss the corresponding signatures at the LHC.Comment: 39 pages, 11 figures, 2 table

Complex Singlet Extension of the Standard Model

We analyze a simple extension of the Standard Model (SM) obtained by adding a complex singlet to the scalar sector (cxSM). We show that the cxSM can contain one or two viable cold dark matter candidates and analyze the conditions on the parameters of the scalar potential that yield the observed relic density. When the cxSM potential contains a global U(1) symmetry that is both softly and spontaneously broken, it contains both a viable dark matter candidate and the ingredients necessary for a strong first order electroweak phase transition as needed for electroweak baryogenesis. We also study the implications of the model for discovery of a Higgs boson at the Large Hadron Collider.Comment: 30 pages, 10 figures, 1 table, PRD versio

Higgs Sector in Extensions of the MSSM

Extensions of the Minimal Supersymmetric Standard Model (MSSM) with additional singlet scalar fields solve the important mu-parameter fine tuning problem of the MSSM. We compute and compare the neutral Higgs boson mass spectra, including one-loop corrections, of the following MSSM extensions: Next-to-Minimal Supersymmetric Standard Model (NMSSM), the nearly-Minimal Supersymmetric Standard Model (nMSSM), and the U(1)'-extended Minimal Supersymmetric Standard Model (UMSSM) by performing scans over model parameters. We find that the Secluded U(1)'-extended Minimal Supersymmetric Standard Model (sMSSM) is identical to the nMSSM if three of the additional scalars decouple. The dominant part of the one-loop corrections are model-independent since the singlet field does not couple to MSSM particles other than the Higgs doublets. Thus, model-dependent parameters enter the masses only at tree-level. We apply constraints from LEP bounds on the Standard Model and MSSM Higgs boson masses and the MSSM chargino mass, the invisible Z decay width, and the Z-Z' mixing angle. Some extended models permit a Higgs boson with mass substantially below the SM LEP limit or above theoretical limits in the MSSM. Ways to differentiate the models via masses, couplings, decays and production of the Higgs bosons are discussed.Comment: 65 pages, 15 figures. Figure replaced and typos corrected. Version to appear in Phys. Rev.

Recoil detection of the lightest neutralino in MSSM singlet extensions

We investigate the correlated predictions of singlet extended MSSM models for direct detection and the cosmological relic density of the lightest neutralino. To illustrate the general effects of the singlet, we take heavy sleptons and squarks. We apply CERN LEP, (g−2)μ, and perturbativity constraints. We find that the WMAP upper bound on the cold dark matter density limits much of the parameter space to regions where the lightest neutralino can be discovered in recoil experiments. The results for the next-to-minimal supersymmetric standard model and U(1)′-extended minimal supersymmetric standard model are typically similar to the MSSM since their light neutralinos have similar compositions and masses. In the nearly minimal supersymmetric standard model the neutralino is often very light and its recoil detection is within the reach of the CDMS II experiment. In general, most points in the parameter spaces of the singlet models we consider are accessible to the WARP experiment

A compilation, tabulation and analysis of spelling errors made by pupils in grades four, five, and six in free writing of sentences using given stimuli words

Thesis (M.A.)--Boston Universit

Neutralino Signatures of the Singlet Extended MSSM

Extending the Higgs sector of the MSSM by the addition of a gauge singlet scalar field can remedy the mu problem. We explore the implications of extended models for both the spectrum of the neutralinos and the cascade decays of the neutralinos and charginos. Extra steps due to light decoupled neutralinos in the cascade decays of both neutralinos and charginos allow an excess of trilepton events compared to the MSSM and the existence of events with higher lepton multiplicity. Additionally, displaced vertices of the chi_2^0 due to small decay widths in some models may be observable.Comment: v1: 19 pages, 6 figures. v2: PLB versio

High White Blood Cell Concentration in the Peripheral Blood Stem Cell Product Can Induce Seizures during Infusion of Autologous Peripheral Blood Stem Cells

Seizures as a complication of the infusion of autologous peripheral blood stem cells (PBSC) are rare. Seizures during infusion of autologous PBSC in 3 of our patients prompted us to review our cell therapy and cytapheresis protocols and procedures. We retrospectively analyzed 159 adult patients collected between January 2006 and July 2009. Patients were collected on either the COBE Spectra (Caridian BCT, Lakewood, CO) cell separator (n = 85) or Fresenius AS (Fresenius Kabi AG, Bad Homburg, Germany) 104 cell separator (n = 74) and mobilized with granulocyte-colony stimulating factor (G-CSF) alone (n = 47), G-CSF and Plerixafor (n = 36), or G-CSF and chemotherapy (n = 76). Patient characteristics (including age, weight, number of collections, volume processed, disease type, and mobilization strategy) did not differ significantly between the COBE and Fresenius cohorts, and adverse effects from infusion were similar except for 3 of 159 patients who experienced seizures upon infusion of PBSC; all 3 were collected on the COBE and had PBSC product white blood cell (WBC) counts of 590 × 103/μL or above. We prospectively correlated WBC counts midcollection, with final WBC counts to identify products with high WBC concentration during cytapheresis. Fifty-one patients had 66 cytapheresis procedures using the COBE, with WBC counts midway and at the end of collection of 287 × 103 ± 150/μL and 273 × 103 ± 144/μL, respectively. Mid-WBC therefore correlated with WBC at the end of the collection. Finally, we prospectively collected mid-WBC from 65 patients who underwent 80 PBSC collections between June 2009 and January 2010 to identify products with midcollection WBC concentration >450 × 103/μL. In those cases, additional autologous plasma was collected at the time of collection to dilute the final product before cryopreservation. Patients who received diluted products experienced no delays in engraftment and no additional seizure episodes occurred

Practitioner Review: effectiveness and mechanisms of change in participatory arts-based programmes for promoting youth mental health and well-being – a systematic review

Background: Participatory arts-based (PAB) programmes refer to a diverse range of community programmes involving active engagement in the creation process that appear helpful to several aspects of children's and young people's (CYP) mental health and well-being. This mixed-methods systematic review synthesises evidence relating to the effectiveness and mechanisms of change in PAB programmes for youth. Method: Studies were identified following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach. Eleven electronic databases were searched for studies of PAB programmes conducted with CYP (aged 4–25 years), which reported mental health and well-being effectiveness outcomes and/or mechanisms of change. A mixed-methods appraisal tool assessed study quality. A narrative synthesis was conducted of effectiveness and challenges in capturing this. Findings relating to reported mechanisms of change were integrated via a metasummary. Results: Twenty-two studies were included. Evidence of effectiveness from quantitative studies was limited by methodological issues. The metasummary identified mechanisms of change resonant with those proposed in talking therapies. Additionally, PAB programmes appear beneficial to CYP by fostering a therapeutic space characterised by subverting restrictive social rules, communitas that is not perceived as coercive, and inviting play and embodied understanding. Conclusions: There is good evidence that there are therapeutic processes in PAB programmes. There is a need for more transdisciplinary work to increase understanding of context–mechanism–outcome pathways, including the role played by different art stimuli and practices. Going forward, transdisciplinary teams are needed to quantify short- and long-term mental health and well-being outcomes and to investigate optimal programme durations in relation to population and need. Such teams would also be best placed to work on resolving inter-disciplinary methodological tensions