Light CP-odd Higgs Boson Research Articles

The search for a light CP-odd Higgs and light dark matter at colliders

The possible existence of a light CP-odd Higgs boson in the NMSSM, mixing with ηb resonances, can yield sizable effects on the bottomonium spectroscopy and decays to be observed at (Super) B factories. On the other hand, recent findings from astroparticle and cosmology favoring a light dark matter constituent with mass about 10 GeV or less cast a new interest into the search for invisible decays of Υ resonances performed ar B factories.

Search for Dimuon Decays of a Light Scalar Boson in Radiative TransitionsΥ→γA0

We search for evidence of a light scalar boson in the radiative decays of the Upsilon(2S) and Upsilon(3S) resonances: Upsilon(2S,3S)-> gamma A0, A0 -> mu^+ mu^-. Such a particle appears in extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212<= m(A0)<= 9.3 GeV in the samples of 99*10^6 Upsilon(2S) and 122*10^6 Upsilon(3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A0. We also limit the dimuon branching fraction of the eta_b meson: BR(eta_b->mu^+mu^-)<0.9% at 90% confidence level.

A light CP-odd Higgs boson and the muon anomalous magnetic moment

We amalgamate the many experimental limits on the ab coupling of a light CP-odd Higgs boson, a, including model-dependence coming from the ratio of the at to the ab coupling. We then employ these limits to analyze the extent to which a light a can make a significant contribution to the discrepancy, Δaμ, between the experimentally observed aμ and that predicted by the standard model. In a ``model-independent'' framework and in the context of a general two-Higgs-doublet model this is a significant possibility. In contrast, the minimal supersymmetric model is too strongly constrained (after combining experimental and theoretical input) to allow a CP-odd-a explanation of Δaμ. The next-to-minimal supersymmetric model allows more freedom and the light a of the model could explain the full Δaμ if 9.2 GeV < ma < 12 GeV, or contribute substantially for larger ma, if tan β is large.

Light CP-Odd Higgs Boson Production Associated with the J/?÷ Meson in the NMSSM

Light CP-Odd Higgs Boson Production Associated with the J/?÷ Meson in the NMSSM

Hunting a light CP-odd non-standard Higgs boson through its tauonic decay at a (Super) B factory

Several scenarios beyond the minimal extension of the Standard Model still allow light non-standard Higgs bosons evading LEP bounds. We examine the mixing between a light CP-odd Higgs boson and ηb states and its implications on a slight (but observable) lepton universality breaking in Upsilon decays to be measured at the percent level at a (Super) B factory.

Light neutralino dark matter in the next-to-minimal supersymmetric standard model

Neutralino dark matter is generally assumed to be relatively heavy, with a mass near the electroweak scale. This does not necessarily need to be the case, however. In the next-to-minimal supersymmetric standard model (NMSSM) and other supersymmetric models with an extended Higgs sector, a very light CP-odd Higgs boson can naturally arise making it possible for a very light neutralino to annihilate efficiently enough to avoid being overproduced in the early Universe. In this article, we explore the characteristics of a supersymmetric model needed to include a very light neutralino, 100 MeV<m{sub {chi}}{sub -tilde1{sup 0}}<20 GeV, using the NMSSM as a prototype. We discuss the most important constraints from Upsilon decays, b{yields}s{gamma}, B{sub s}{yields}{mu}{sup +}{mu}{sup -} and the magnetic moment of the muon, and find that a light bino or singlino neutralino is allowed, and can be generated with the appropriate relic density. It has previously been shown that the positive detection of dark matter claimed by the DAMA collaboration can be reconciled with other direct dark matter experiments such as CDMS II if the dark matter particle is rather light, between about 6 and 9 GeV. A singlino or binolike neutralino could easily fall within this range of massesmore » within the NMSSM. Additionally, models with sub-GeV neutralinos may be capable of generating the 511 keV gamma-ray emission observed from the galactic bulge by the INTEGRAL/SPI experiment. We also point out measurements which can be performed immediately at CLEO, BABAR, and Belle using existing data to discover or significantly constrain this scenario.« less

Hints of new physics in bottomonium decays and spectroscopy

A non-standard light CP-odd Higgs boson could induce a slight (but observable) lepton universality breakdown in Upsilon leptonic decays. Moreover, the mixing between such a pseudoscalar Higgs and $\eta_b$ states might shift the mass levels of the latter, thereby changing the values of the $m_{\Upsilon(nS)}-m_{\eta_b(nS)}$ splittings predicted in the standard model. Besides, also the $\eta_b$ width could be broader than expected, with potentially negative consequences for its discovery in both $e^+e^-$ and hadron colliders.

Electroweak baryogenesis and dark matter in a minimal extension of the MSSM

We examine the possibility of electroweak baryogenesis and dark matter in the nMSSM, a minimal extension of the MSSM with a singlet field. This extension avoids the usual domain wall problem of the NMSSM, and also appears as the low energy theory in models of dynamical electroweak symmetry breaking with a so-called fat-Higgs boson. We demonstrate that a strong, first order electroweak phase transition, necessary for electroweak baryogenesis, may arise in regions of parameter space where the lightest neutralino provides an acceptable dark matter candidate. We investigate the parameter space in which these two properties are fulfilled and discuss the resulting phenomenology. In particular, we show that there are always two light CP-even and one light CP-odd Higgs bosons with masses smaller than about 250 GeV. Moreover, in order to obtain a realistic relic density, the lightest neutralino mass tends to be smaller than $M_Z/2$, in which case the lightest Higgs boson decays predominantly into neutralinos.

Higgs-boson production associated with a bottom quark at hadron colliders with supersymmetric QCD corrections

The Higgs boson production pp(p (p) over bar)-->bh+X via bg-->bh at hadron colliders, which may be an important channel for testing the bottom quark Yukawa coupling, is subject to large supersymmetric quantum corrections. In this work the one-loop supersymmetric (SUSY) QCD corrections to this process are evaluated and are found to be quite sizable in some parameter space. We also study the behavior of the corrections in the limit of heavy SUSY masses and find the remnant effects of SUSY QCD. These remnant effects, which are left over in the Higgs sector by the heavy sparticles, are found to be so sizable (for a light CP-odd Higgs boson and large tan beta) that they might be observable in future experiments. The exploration of such remnant effects is important for probing SUSY, especially in the case that the sparticles are too heavy (above TeV) to be directly discovered in future experiments.