Alexandre Alves

The dark Z′ portal: direct, indirect and collider searches

A bstractWe perform a detailed study of the dark Z′ portal using a generic parametrization of the Z′-quarks couplings, both for light (8-15) GeV and heavy (100-1000) GeV dark matter scenarios. We present a comprehensive study of the collider phenomenology including jet clustering, hadronization, and detector artifacts, which allows us to derive accurate bounds from the search for new resonances in dijet events and from mono-jet events in the LHC 7 TeV, LHC 8 TeV, and Tevatron 1.96 TeV data. We also compute the dark matter relic abundance, the relevant scattering cross sections and pair-annihilation spectrum, and compare our results with the current PLANCK, Fermi-LAT and XENON100/LUX bounds. Lastly, we highlight the importance of complementary searches for dark matter, and outline the excluded versus still viable parameter space regions of the dark Z′ portal.

The 750 GeV S-cion: Where else should we look for it?

Abstract The resonance S at ∼ 750 xa0GeV in the diphoton channel observed by ATLAS and CMS, if it holds up, is almost certainly the (S)cion of a larger dynasty in a UV completion that may very well be connected to the hierarchy problem. At this stage, however, an effective field theory framework provides a useful way to parametrize searches for this resonance in other channels. Assuming that the excess is due to a new scalar or pseudoscalar boson, we study associated production of S (“S-strahlung”) at the LHC and propose searches in several clean channels like γ γ l l , γ γ l E T and l l l γ E T to probe dimension-5 operators coupling S to Standard Model gauge bosons. We consider a range of widths for S, from 5 GeV to 45 GeV, and find that the three channels probe complementary regions of parameter space and the suppression scale Λ. The finding of most immediate relevance is that with 3 xa0fb − 1 , the LHC might already reveal new excesses in the γ γ l l channel and a 5 (3) σ discovery may already be possible after collecting 65 (25) fb − 1 of data with l l l γ E T events if the scale of the new physics is within ∼ 9 xa0TeV for couplings respecting 8 TeV LHC bounds and compatible with the observed excess in diphotons for a wide resonance as suggested by the ATLAS Collaboration. Beyond the EFT parametrization, we found realizations of models with heavy vector-like quarks and leptons which can simultaneously fit the diphoton excess and be discovered in the channels proposed here.

Effective field theory approach to the Galactic Center gamma-ray excess

We explore the possibility of explaining a gamma-ray excess in the Galactic center, originally pointed out by Hooper, collaborators, and other groups, in an effective field theory framework. We assume that dark matter annihilation is mediated by particles heavy enough to be integrated out, and that such particles couple to all quark families. We calculate the effective coupling required to explain the annihilation signal in the Galactic center, and compare with bounds from direct detection, collider searches, and the requirement that the dark matter particle make up the appropriate fraction of the universal energy budget. We find that only a very small set of operators can explain the gamma-ray excess while being consistent with other constraints. Specifically, for scalar dark matter the viable options are one scalar-type coupling to quarks and one interaction with gluons, while for fermionic (Dirac) dark matter the viable options are two scalar-type dimension-7 operators or a dimension-6 vector-type operator. In all cases, future searches with the Large Hadron Collider should probe the relevant operators’ effective energy scale, while all viable interactions should escape direct detection experiments. 1 ar X iv :1 40 3. 50 27 v1 [ he pph ] 2 0 M ar 2 01 4

Dirac-fermionic dark matter in U(1)X models

A bstractWe study a number of U(1)X models featuring a Dirac fermion dark matter particle. We perform a comprehensive analysis which includes the study of corrections to the muon magnetic moment, dilepton searches with LHC data, as well as direct and indirect dark matter detection constraints. We consider four different coupling structures, namely U(1)B−L, U(1)d−u, U(1)universal, and U110+5¯

Incremental shuttle and six-minute walking tests in the assessment of functional capacity in chronic heart failure

mathrm{U}{(1)}_{10+overline{5}}

Searching for Elko dark matter spinors at the CERN LHC

, all motivated by compelling extensions to the standard model. We outline the viable and excluded regions of parameter space using a large set of probes. Our key findings are that (i) the combination of direct detection and collider constraints rule out dark matter particle masses lighter than ∼ 1 TeV, unless rather suppressed Z′-fermion couplings exist, and that (ii) for several of the models under consideration, collider constraints rule out Z′ masses up to ∼ 3 TeV. Lastly, we show that we can accommodate the recent Diboson excess reported by ATLAS collaboration within the U(1)d−u model.

Collider and Dark Matter Searches in the Inert Doublet Model from Peccei-Quinn Symmetry

Z 0 gauge bosons arise in many particle physics models as mediators between the dark and visible sectors. We exploit dark matter complementarity and derive stringent and robust collider, direct and indirect constraints, as well as limits from the muon magnetic moment. We rule out almost the entire region of the parameter space that yields the right dark matter thermal relic abundance, using a generic parametrization of the Z 0 -fermion couplings normalized to the Standard Model Z-fermion couplings for dark matter masses in the 8 GeV-5 TeV range. We conclude that mediators lighter than 2:1 TeV are excluded regardless of the DM mass, and that depending on theZ 0 fermion coupling strength much heavier masses are needed to reproduce the DM thermal relic abundance while avoiding existing limits.

Augury of darkness: the low-mass dark Z ′ portal

BACKGROUNDnThe incremental shuttle test presents some theoretical advantages over the six-minute walk test in chronic heart failure (CHF), including better standardization and less dependency on collaboration.nnnOBJECTIVESnThe present study evaluated test-retest repeatability, test accuracy in predicting a peak oxygen consumption (VO(2)) of 14 mL/kg/min or less, as well as the prognostic value of both walking tests in stable CHF patients.nnnMETHODSnSixty-three patients (44 men; New York Heart Association functional class II to IV) underwent an incremental treadmill exercise test and, on another day, the walk test in duplicate.nnnRESULTSnPatients showed well-preserved functional capacity according to the distance walked in both tests (six-minute walk test 491+/-94 m versus incremental shuttle walk test 422+/-119 m; P<0.001). Interestingly, the six-minute and incremental shuttle walk test differences in distance walked were higher in more disabled patients. The mean bias +/-95% CI of the within-test differences were similar (7+/-40 m and 8+/-45 m, respectively). Peak VO(2), but not distance walked in either test, was associated with survival (P<0.05).nnnCONCLUSIONSnThe incremental shuttle walk test showed similar repeatability and accuracy in estimating peak VO(2) compared with the six-minute walk test in CHF patients. Direct measurement of peak VO(2), however, remains superior to either walking test in predicting survival--at least in patients with well-preserved functional capacity.