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.

We examine the capability of a √ s = 2 TeV Tevatron pp collider to discover supersymmetry, given a luminosity upgrade to amass 25 f b −1 of data. We compare with the corresponding reach of the Tevatron Main Injector (1 f b −1 of data). Working within the framework of minimal supergravity with gauge coupling unification and radiative electroweak symmetry breaking, we first calculate the regions of parameter space accessible via the clean trilepton signal from W 1 Z 2 → 3ℓ + E / T production, with detailed event generation of both signal and major physics backgrounds. The trilepton signal can allow equivalent gluino masses of up to mg ∼ 600 − 700 GeV to be probed if m 0 is small. If m 0 is large, then mg ∼ 500 GeV can be probed for µ < 0; however, for µ > 0 and large values of m 0 , the rate for Z 2 → Z 1 ℓl is suppressed by interference effects, and there is no reach in this channel. We also examine regions where the signal from W 1 W 1 → ℓl + E / T is detectable. Although this signal is background limited, it is observable in some regions where the clean trilepton signal is too small. Finally, the signal W 1 Z 2 → jets + ℓl + E / T can confirm the clean trilepton signal in a substantial subset of the parameter space where the trilepton signal can be seen. We note that although the clean trilepton signal may allow Tevatron experiments to identify signals in regions of parameter space beyond the reach of LEP II, the dilepton channels generally probe much the same region as LEP II.

The Rapid Communications section is intended for the accelerated publication of important new results. Since manuscripts submitted to this section are given priority treatment both in the editorial ofice and in production, authors should explain in their submittal letter why the work justifies this special handling. A Rapid Communication should be no longer than 3% printed pages and must be accompanied by an abstract.We determine the contribution to pp-ZZ+ X from gluon +gluon-ZZ by evaluating the relevant box diagrams.The intermediate gauge bosons of the standard model ( W * , z ) have been produced in hadron colliders. Their production in supercolliders will be used to study the trilinear gauge coupling, to look for rare decays, to look for extensions of the standard model, and to search for the Higgs boson. The rate of production of pairs of gauge bosons in the parton model is not accurately known because, although the calculation of quark-antiquark annihilation qq+ ZZ, W + w -is trivial, the calculation of gluon fusion gg+ ZZ, W + w -proceeds through box diagrams, and boxes are notoriously difficult. The only previous calculation of gg-ZZ was by Pumplin, Repko, and Kane,' who calculated the imaginary parts of the longitudinal amplitudes. In this paper, we report the first full calculation of gg-ZZ and its contribution toSome parton processes which proceed only through box diagrams have been calculated. A (probably incomplete)Explicit evaluation of the box diagram is avoided for each of these processes by using a Mandelstam representation as developed for photon-photon scattering by DeTollis. Unfortunately gg--+ ZZ cannot be done this way because the usual form of the Mandelstam representation is not valid when more than one of the external particles has a mass larger than the mass of the internal lines of the box. 'In 1979 Veltman addressed the problems of one-loop diagrams by clearly explaining techniques for performing the integrals involveds and then by developing a very sophisticated computer code, called FORMF, to evaluate all the needed integrals. The use of the code is described in a paper with a as sari no.^ This is the method we have used to calculate the gluon-gluon contribution to pp -ZZ +X.We checked Veltman's code in three ways. (1) Before even attempting gg-ZZ we did a complete calculation of photon-photon scattering yy-y y , and compared it with the classic results of Karplus and ~e u m a n " for scattering at right angles. (2) All the four-point integrals can be derived from the integrals with no momenta in the numerator and one, two, three, or four factors in the denominator. We explicitly calculated the most difficult of these, the one with four factors in the denominator, and our result agrees with that given by the code. (3) After calculating gg-ZZ we checked gauge invariance by numerically replacing the polarization vector of one of the gluons by its momentum. The result was not exactly zero because of numerical limitations but was always less than of the result for the physical process. T...

A two Higgs doublet model with special Yukawa interactions for the top quark and a softly broken discrete symmetry in the Higgs potential is proposed. In this model, the top quark is much heavier than the other quarks and leptons because it couples to a Higgs doublet with a much larger vacuum expectation value. The electric dipole moment (EDM) of the electron is evaluated with loop diagrams of the third generation fermions as well as the charm quark. The electron EDM is significantly enhanced for a naturally large tan β ≡ |v 2 |/|v 1 |.