A general two Higgs doublet model (2HDM) is adopted to study the signature of flavor changing neutral Higgs (FCNH) decay φ 0 → tc +tc, where φ 0 could be a CP-even scalar (H 0 ) or a CP-odd pseudoscalar (A 0 ). Measurement of the light 125 GeV neutral Higgs boson (h 0 ) couplings at the Large Hadron Collider (LHC) favor the decoupling limit or the alignment limit of a 2HDM, in which gauge boson and diagonal fermion couplings of h 0 approach Standard Model values. In such limit, FCNH couplings of h 0 are naturally suppressed by a small mixing parameter cos(β − α), while the off-diagonal couplings of heavier neutral scalars φ 0 are sustained by sin(β − α) ∼ 1. We study physics background from dominant processes with realistic acceptance cuts and tagging efficiencies. Promising results are found for the LHC running at 13 or 14 TeV collision energies.

The protein kinase ATM is a master regulator of the DNA damage response but also responds directly to oxidative stress. Loss of ATM causes Ataxia telangiectasia, a neurodegenerative disorder with pleiotropic symptoms that include cerebellar dysfunction, cancer, diabetes, and premature aging. Here, we genetically separated DNA damage activation of ATM from oxidative activation using separation-of-function mutations. We found that deficiency in ATM activation by Mre11-Rad50-Nbs1 and DNA double-strand breaks resulted in loss of cell viability, checkpoint activation, and DNA end resection in response to DNA damage. In contrast, loss of oxidative activation of ATM had minimal effects on DNA damage-related outcomes but blocked ATM-mediated initiation of checkpoint responses after oxidative stress and resulted in deficiencies in mitochondrial function and autophagy. In addition, expression of ATM lacking oxidative activation generates widespread protein aggregation. These results indicate a direct relationship between the mechanism of ATM activation and its effects on cellular metabolism and DNA damage responses in human cells and implicates ATM in the control of protein homeostasis.

In the Kaluza-Klein (KK) scenario with n large extra dimensions where gravity propagates in the 4+n dimensional bulk of spacetime while gauge and matter fields are confined to a four dimensional subspace, the light graviton KK modes can be produced in the Sun, red giants and supernovae. We study the energy-loss rates through photon-photon annihilation, electron-positron annihilation, gravi-Compton-Primakoff scattering, gravi-bremsstrahlung and nucleon-nucleon bremsstrahlung, and derive lower limits to the string scale M S . The most stringent lower limit obtained from SN1987A leads to M S > 30−130 TeV (2.1−9.3 TeV) for the case of two (three) large extra dimensions.

We have examined the production of a charged Higgs boson in association with a W boson at high-energy hadron colliders, i.e., pp -W* H +X, and find that the production rates can be large.The various subprocesses which contribute to this mechanism at the tree and one-loop levels are compared and we find that quark annihilation b6,tT-W'H ' is dominant. Production via gluongluon fusion, which proceeds through box and triangle diagrams, is also found to yield a significant contribution. We also compare our results with those obtained in rank-5 E6 models for this process.One of the least understood aspects of the standard model (SM) is the Higgs sector which is responsible for spontaneous symmetry breaking (SSB) and the generation of masses for the fermions and gauge bosons. Whereas the SM leads to a single Higgs scalar after SSB, extensions of the SM can lead to additional physical spin-zero fields. In the two-Higgs-doublet extension, after SSB, there remains a pair of singly charged Higgs bosons, two neutral scalars, and a neutral pseudoscalar. Clearly, the detection of the SM Higgs boson, or the Higgs fields of any extended model, will greatly clarify our knowledge of this mysterious sector of electroweak gauge theories.Future colliders, such as the Superconducting Super Collider (SSC) and the C E R N Large Hadron Collider (LHC) are being designed in order to explore the nature of the Higgs sector. Even at these high-energy colliders the production rate for Higgs bosons of all kinds is usually small and signatures are not always easily detected even when they are produced. Although the production rates for both neutral and charged Higgs bosons are comparable at these high-energy hadron colliders, the neutral Higgs boson is much easier to identify. This is due to the fact that the neutral Higgs boson has a more spectacular signature since it may decay to gauge-boson pairs, while the charged Higgs boson decays dominantly into heavyfermion pairs. One process which may be used to search for the charged Higgs boson which seems promising is the production of a charged Higgs boson in association with a W gauge boson: pp -W"H +X. The subsequent decays of the W would help identify the process as one to study for the presence of a charged Higgs boson. In this paper we examine this reaction and the various subprocesses which contribute to it in the two-Higgsdoublet extension of the SM. As will be discussed below, the general two-Higgs-doublet model contains too many independent parameters to analyze in a straightforward manner. Therefore, we will limit our discussion to the subset of models which satisfy the mass and mixing-angle relationships of the minimal supersymmetric model when calculating loop-order contributions to W'H ' production. W*H + production may also occur in superstringinspired E6 theories due to the nonvanishing of the FIG. 1. Tree-level Feynman diagrams contributing to the bb; tr-W + H -process.40 787 -

We investigate the prospects for the detectability of the Higgs bosons of the minimal supersymmetric model (MSSM) at future colliders. First we delineate regions of MSSM parameter space where the various Higgs bosons may be observable at the CERN e+e-collider LEP 200 or hadron super-collider~, assuming (as usual) that Higgs-boson decay modes to supersymmetric particles are not allowed. We find that, even with optimistic assumptions of detector capabilities, there exist regions of parameter space where none of the Higgs bosons are visible. Next, we show that there are substantial regions of parameter space where rates for Higgs-boson decays to supersymmetric particles are large, and even dominant. These decays reduce the rates for conventional Higgs-boson signatures, thus making conventional detection of Higgs bosons even more difficult. However, a number of new, promising modes for Higgs-boson detection have opened up. These include a "gold-plated" Higgs scalar or pseudoscalar decay to four leptons plus missing energy which may make possible a precise mass measurement of the lightest and second lightest neutralino. Furthermore, rare decays of the top quark into a b quark plus three leptons may be visible, and signal charged-Higgs-boson decays to a chargino plus neutralino.