1,722,152 research outputs found
Detection of heavy charged Higgs bosons in e+ e- -> t anti-b H- production at future linear colliders
No full textHeavy charged Higgs bosons (H±) of a Type II 2-Higgs doublet model (2HDM) can be detected at future electron–positron Linear Colliders (LCs) even when their mass is larger than half the collider energy. The single Higgs mode e+e- → t¯bH-+ c.c. → 4b+jj+ℓ+pmissT (where j represents a jet and with ℓ = e,µ) contributes to extend the discovery reach of H± states into the mass region MH± √s/2, where the well studied pair production channel e+e- → H-H+ is no longer available. With a technique that allows one to reconstruct the neutrino four-momentum in the decay t → bW+ →bℓ+ν, one can suppress the initially overwhelming main irreducible background due to e+e- → t¯tb¯b (via a gluon splitting into b¯b pairs) to a negligible level. However, for currently foreseen luminosities, one can establish a statistically significant H± signal only over a rather limited mass region, of 20 GeV or so, beyond MH± ~ √s/2, for very large or very small values of tan β and provided high b-tagging efficiency can be achieved
Six-fermions (and more) studies
No full textWe review the available event generators suited for multi-fermion final state production in the context of physics studies at a future Linear Collider (LC)
Matrix-element corrections to parton shower simulations for Higgs hadroproduction
No full textWe implement matrix-element corrections to HERWIG parton shower simulations for Standard Model Higgs boson production at hadron colliders. We study the Higgs transverse momentum distribution and compare different versions of HERWIG and resummed calculations. The HERWIG results exhibit a remarkable improvement as many more events are generated at large transverse momentum after the inclusion of matrix-element corrections
Di-photon Higgs signals at the LHC in the next-to-minimal supersymmetric standard model
No full textThe NMSSM contains a Higgs singlet in addition to the two Higgs doublets typical of the MSSM, thus resulting in a total of seven physical Higgs mass states. Therefore, the phenomenology of the NMSSM Higgs sector can differ considerably from that of the MSSM, and there are good prospects of finding in regions of the NMSSM parameter space Higgs signals that cannot be reproduced in the MSSM. We examined here the two-photon decay mode of a Higgs boson and found that up to three neutral Higgs states, heavy and/or light, could be simultaneously observable at the LHC, a possibility precluded to the MSSM. There are also some possibilities that only the lightest NMSSM Higgs boson be detectable via this mode, with a mass beyond the upper limit of the corresponding MSSM state, thus also allowing one to distinguish between the two scenarios. However, in most of the NMSSM parameter space the configurations of the non-minimal model are not very different from those arising in the minimal case
The B − L supersymmetric standard model with inverse seesaw at the large hadron collider
No full textWe review the TeV scale extension of the Minimal Supersymmetric Standard Model (BLSSM) where an inverse seesaw mechanism of light neutrino mass generation is naturally implemented and concentrate on its hallmark manifestations at the Large Hadron Collider (LHC)
Clinical prognosis in BRAF-mutated PTC
No full textBRAF mutation has recently emerged as a potential prognostic marker for papillary thyroid carcinoma (PTC) due to several studies suggesting that it may condition the development of tumors with aggressive behavior. A study of the phenotypes of thyroid follicular cell lines and transgenic mice characterized by targeted expression of BRAF mutation indicates that, at variance with RET/PTC rearrangement, it induces or facilitates genomic instability and higher invasiveness and eventually deeper tumor de-differentiation and more significant suppression of apoptosis. An analysis of differential gene expression of PTCs harboring BRAF mutation versus PTCs characterized by other genetic alterations shows an important impairment of the expression of genes related to intra-thyroidal iodine metabolism machinery, up-regulation of Glut-1 mRNA, methylation-induced gene silencing of tumor suppressor genes and up-regulation of pro-angiogenetic proteins such as VEGF. Correlation of BRAF mutation with PTC clinico-pathological features yields controversial results, with several studies showing the association with unfavourable clinico-pathological qualities, while others do not confirm the findings. This review will summarize the studies in favor of or in contrast with a role of BRAF mutation as a prognostic marker in PTC. We will also indicate what information we still need in order to routinely introduce this indicator in clinical practice
ADD and MLS signals in top-antitop final states
Full text linkWe study top-(anti)quark pair production at the Tevatron and
LHC in the context of the Minimal Length Scenario (MLS) of the Arkani-Hamed, Dimopoulos and Dvali (ADD) model of extra dimensions (XDs). We show that sizable effects onto both the integrated and differential cross section due to graviton mediation are expected for a String scale, MS, of O(1–10TeV) and several XDs, δ, all compatible with current experimental constraints. Potential limits on MS are
extracted. We also highlight clear phenomenological differences between a simple ADD scenario and its modification based on using the MLS as a natural regulator
for divergent amplitudes of virtual KK graviton exchange
Probing the light neutral Higgs boson scenario of the CP- violating MSSM Higgs sector at the LHC
No full textIn the CP-violating minimal supersymmetric standard model (MSSM), for certain values of the CP-violating phases associated to the universal trilinear couplings (At,Ab) and the gluino mass (M˜g), e.g., ΦCP = 60º or 90º, for MH+ ≲ 140 GeV and tan β ~ 2–5, the lightest Higgs boson mass (MH1) is ≲ 50 GeV. This mass interval is still allowed by results of standard LEP Higgs searches because of a strongly suppressed H1ZZ coupling. However, in the same region of parameter space in which these two conditions occur, the H1H∓W± coupling is enhanced because the two mentioned sets of couplings satisfy a sum rule. In this paper we probe such a light Higgs scenario at the Large Hadron Collider (LHC) by studying H±H1 associate production, leading to a 4b+ ℓ± +ET signal. We show that the latter is readily accessible at the CERN hadron collider, upon the application of suitable selection cuts against the standard model (SM) backgrounds. Our part on level Monte Carlo (MC) analysis yields ~ 15–45 signal events, completely free of SM background, for L = 10–30 fb-1 of accumulated luminosity, after taking into account the overall efficiency for tagging four b-jets
From old to new particles: a simple symmetry is guiding us
No full textThere exists one experimental result that cannot be explained by the Standard Model (SM), the current theoretical framework for particle physics: non-zero masses for the neutrinos (elementary particles travelling close to light speed, electrically neutral and weakly interacting). The SM assumes that they are massless. Therefore, particle physicists are now exploring new physics beyond the SM. There is strong anticipation that we are about to unravel it, in the form of new matter and/or forces, at the Large Hadron Collider (LHC), presently running at CERN. We discuss a minimal extension of the SM, based on a somewhat larger version of its symmetry structure and particle content, that can naturally explain the existence of neutrino masses while also predicting novel signals accessible at the LHC, including a light Higgs boson, as evidenced by current data
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