118545965
Low-mass Higgs bosons in the NMSSM and their LHC implications
A bstractWe study the Higgs sector of the Next to Minimal Supersymmetric Standard Model (NMSSM) in light of the discovery of the SM-like Higgs boson at the LHC. We perform a broad scan over the NMSSM parameter space and identify the regions that are consistent with current Higgs search results at colliders. In contrast to the commonly studied “decoupling” scenario in the literature where the Minimal Supersymmetric Standard Model CP-odd Higgs boson mass is large mA ≫ mZ , we pay particular attention to the light Higgs states in the case when mA ≲ 2mZ . The Higgs bosons in the NMSSM, namely three CP-even states, two CP-odd states, and two charged Higgs states, could all be rather light, near or below the electroweak scale, although the singlet-like states can be heavier. The SM-like Higgs boson could be either the lightest CP-even scalar or the second lightest CP-even scalar, but is unlikely to be the heaviest scalar. These NMSSM parameter regions have unique properties and offer rich phenomenology. The decay branching fractions for the SM-like Higgs boson may be modified appreciably. The correlations of γγ/V V and $ {VV \left/ {{b\overline{b}}} \right.} $ can be substantially altered. The new Higgs bosons may be readily produced at the LHC and may decay to non-standard distinctive final states, most notably a pair of Higgs bosons when kinematically accessible. We evaluate the production and decay of the Higgs bosons and comment on further searches at the LHC to probe the Higgs sector of the NMSSM.
119220539
Potential precision of a direct measurement of the Higgs boson total width at a muon collider
In the light of the discovery of a 126 GeV Standard-Model-like Higgs boson at the LHC, we evaluate the achievable accuracies for direct measurements of the width, mass, and the $s$-channel resonant production cross section of the Higgs boson at a proposed muon collider. We find that with a beam energy resolution of $R=0.01%$ (0.003%) and integrated luminosity of $0.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ ($1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$), a muon collider would enable us to determine the Standard-Model-like Higgs width to $\ifmmode\pm\else\textpm\fi{}0.35\text{ }\text{ }\mathrm{MeV}$ ($\ifmmode\pm\else\textpm\fi{}0.15\text{ }\text{ }\mathrm{MeV}$) by combining two complementary channels of the $W{W}^{*}$ and $b\overline{b}$ final states. A non-Standard-Model Higgs with a broader width is also studied. The unparalleled accuracy potentially attainable at a muon collider would test the Higgs interactions to a high precision.
117360716
Diagnosis of a New Neutral Gauge Boson at the LHC and ILC for Snowmass 2013
A U(1)' or Z' is generic in many scenarios of physics beyond the Standard Model, such as string theory compactifications, GUTs, extra-dimensions, compositeness, dynamical electroweak symmetry breaking, dark-sector models, etc. We study the potential of probing a TeV-scale Z' with electroweak couplings in future experiments. In particular, we focus on two scenarios: (1) If a Z' is discovered at the LHC, what is the potential of measuring its mass and width and to distinguish between benchmark models utilizing various observables, especially asymmetries, at a high luminosity LHC and the ILC. (2) If the Z' is not accessible as a clear resonance signal, what is the exclusion reach at the ILC.
124189092
Working Group Report: New Particles, Forces, and Dimensions
120893290
Working Group Report: Higgs Boson
59333781
The Case for a Muon Collider Higgs Factory
Author(s): Alexahin, Y; Ankenbrandt, CM; Cline, DB; Conway, A; Cummings, MA; Benedetto, VD; Eichten, E; Delahaye, J-P; Gatto, C; Grinstein, B; Gunion, J; Han, T; Hanson, G; Hill, CT; Ignatov, F; Johnson, RP; Lebedev, V; Lederman, LM; Lipton, R; Liu, Z; Markiewicz, T; Mazzacane, A; Mokhov, N; Nagaitsev, S; Neuffer, D; Palmer, M; Purohit, MV; Raja, R; Rubbia, C; Striganov, S; Summers, D; Terentiev, N; Wenzel, H | Abstract: We propose the construction of a compact Muon Collider Higgs Factory. Such a machine can produce up to \sim 14,000 at 8\times 10^{31} cm^-2 sec^-1 clean Higgs events per year, enabling the most precise possible measurement of the mass, width and Higgs-Yukawa coupling constants.
204860499
Flavour independent search for neutral Higgs bosons at LEP
Abstract A flavour independent search for the CP-even and CP-odd neutral Higgs bosons h and A is performed in 624 pb −1 of data collected with the L3 detector at LEP at centre-of-mass energies between 189 and 209 GeV . Higgs boson production through the e + e − →Zh and the e + e − →hA processes is considered and decays of the Higgs bosons into hadrons are studied. No significant signal is observed and 95% confidence level limits on the hZZ and hAZ couplings are derived as a function of the Higgs boson masses. Assuming the Standard Model cross section for the Higgs-strahlung process and a 100% branching fraction into hadrons, a 95% confidence level lower limit on the mass of the Higgs boson is set at 110.3 GeV.
124921771
Search for neutral Higgs boson production through the process e+ e- --> Z* H0
Abstract The results of the searches for neutral Higgs boson production in the process e + e − → Z ∗ H 0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z 0 decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L. These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e + e − → Z ∗ h 0 are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state.
67766264
PAMELA Positron Excess as a Signal from the Hidden Sector
The recent positron excess observed in the PAMELA satellite experiment strengthens previous experimental findings. We give here an analysis of this excess in the framework of the Stueckelberg extension of the standard model which includes an extra $U(1{)}_{X}$ gauge field and matter in the hidden sector. Such matter can produce the right amount of dark matter consistent with the Wilkinson Microwave Anisotropy Probe (WMAP) constraints. Assuming the hidden sector matter to be Dirac fermions it is shown that their annihilation can produce the positron excess with the right positron energy dependence seen in the HEAT, AMS, and the PAMELA experiments. The predictions of the $\overline{p}/p$ flux ratio also fit the data.
8142176
Gluino NLSP, dark matter via gluino coannihilation, and LHC signatures
The possibility that the gluino is the next to the lightest supersymmetric particle (NLSP) is discussed and it is shown that this situation arises in nonuniversal supergravity models within a significant part of the parameter space compatible with all known experimental bounds. It is then shown that the gluino NLSP (GNLSP) models lead to a compressed sfermion spectrum with the sleptons often heavier than the squarks at least for the first two generations. The relic density here is governed by gluino coannihilation which is responsible for a relatively small mass splitting between the gluino and the neutralino masses. Thus the GNLSP class of models is very predictive first because the supersymmetry (SUSY) production cross sections at the CERN LHC are dominated by gluino production and second because the gluino production itself proceeds dominantly through a single channel which allows for a direct determination of the gluino mass and an indirect determination of the neutralino mass due to a linear relation between these two masses which is highly constrained by coannihilation. A detailed analysis of these models shows that the jet production and tagged b jets from the gluino production can be discriminated from the standard model background with appropriate cuts.more » It is found that the GNLSP models can be tested with just 10 fb{sup -1} of integrated luminosity and may therefore be checked with low luminosity runs in the first data at the LHC. Thus if a GNLSP model is realized, the LHC will turn into a gluino factory through a profuse production of gluinos with typically only a small fraction < or approx. 5% of total SUSY events arising from other production modes over the allowed GNLSP model parameter space.« less
209843256
Search for branons at LEP
Abstract We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons . Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e + e − collisions at centre-of-mass energies 2 = 189 – 209  GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103  GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded.