5169671
Collision and Symmetry Breaking in the Transition to Strange Nonchaotic Attractors
Strange nonchaotic attractors (SNAs) can be created due to the collision of an invariant curve with itself. This novel "homoclinic" transition to SNAs occurs in quasiperiodically driven maps which derive from the discrete Schrodinger equation for a particle in a quasiperiodic potential. In the classical dynamics, there is a transition from torus attractors to SNAs, which, in the quantum system, is manifest as the localization transition. This equivalence provides new insight into a variety of properties of SNAs, including its fractal measure. Further, there is a symmetry breaking associated with the creation of SNAs which rigorously shows that the Lyapunov exponent is nonpositive. We show that these characteristics associated with the appearance of SNA are robust and occur in a large class of systems.
119302337
Gauge-Higgs unification, neutrino masses, and dark matter in warped extra dimensions
Gauge-Higgs unification in warped extra dimensions provides an attractive solution to the hierarchy problem. The extension of the standard model gauge symmetry to SO(5)xU(1){sub X} allows the incorporation of the custodial symmetry SU(2){sub R} plus a Higgs boson doublet with the right quantum numbers under the gauge group. In the minimal model, the Higgs mass is in the range 110-150 GeV, while a light Kaluza-Klein excitation of the top quark appears in the spectrum, providing agreement with precision electroweak measurements and a possible test of the model at a high luminosity LHC. The extension of the model to the lepton sector has several interesting features. We discuss the conditions necessary to obtain realistic charged lepton and neutrino masses. After the addition of an exchange symmetry in the bulk, we show that the odd neutrino Kaluza-Klein modes provide a realistic dark-matter candidate, with a mass of the order of 1 TeV, which will be probed by direct dark-matter detection experiments in the near future.
118481994
Vacuum stability and Higgs diphoton decays in the MSSM
A bstractCurrent Higgs data at the Large Hadron Collider is compatible with a SM signal at the 2σ level, but the central value of the signal strength in the diphoton channel is enhanced with respect to the SM expectation. If the enhancement resides in the diphoton partial decay width, the data could be accommodated in the Minimally Super-symmetric Standard Model (MSSM) with highly mixed light staus. We revisit the issue of vacuum instability induced by large mixing in the stau sector, including effects of a radiatively-corrected tau Yukawa coupling. Further, we emphasize the importance of taking into account the tan β dependence in the stability bound. While the metastability of the Universe constrains the possible enhancement in the Higgs to diphoton decay width in the light stau scenario, an increase of the order of 50% can be achieved in the region of large tan β. Larger enhancements may be obtained, but would require values of tan β associated with non-perturbative values of the tau Yukawa coupling at scales below the GUT scale, thereby implying the presence of new physics beyond the MSSM.
12291219
A Heavy Higgs and a Light Sneutrino NLSP in the MSSM with Enhanced SU(2) D-terms
The Minimal Supersymmetric extension of the Standard Model provides a solution to the hierarchy problem and leads to the presence of a light Higgs. A Higgs boson with mass above the present experimental bound may only be obtained for relatively heavy third generation squarks, requiring a precise, somewhat unnatural balance between different contributions to the effective Higgs mass parameter. It was recently noticed that somewhat heavier Higgs bosons, which are naturally beyond the LEP bound, may be obtained by enhanced weak SU(2) Dterms. Such contributions appear in models with an enhanced electroweak gauge symmetry, provided the supersymmetry breaking masses associated with the scalars responsible for the breakdown of the enhanced gauge symmetry group to the Standard Model one, are larger than the enhanced symmetry breaking scale. In this article we emphasize that the enhanced SU(2) D-terms will not only raise the Higgs boson mass but also affect the spectrum of the nonstandard Higgs bosons, sleptons and squarks, which therefore provide a natural contribution to the T parameter, compensating for the negative one coming from the heavy Higgs boson. The sleptons and non-standard Higgs bosons of these models, in particular, may act in a way similar to the so-called inert Higgs doublet. The phenomenological properties of these models are emphasized and possible cosmological implications as well as collider signatures are described.
15780949
Collider phenomenology of gauge-Higgs unification scenarios in warped extra dimensions
We compute the couplings of the zero modes and first excited states of gluons, W's, Z gauge bosons, as well as the Higgs, to the zero modes and first excited states of the third generation quarks, in a Randall-Sundrum Gauge-Higgs unification scenario based on a bulk SO(5)xU(1){sub X} gauge symmetry, with gauge and fermion fields propagating in the bulk. Using the parameter space consistent with electroweak precision tests and radiative electroweak symmetry breaking, we study numerically the dependence of these couplings on the parameters of our model. Furthermore, after emphasizing the presence of light excited states of the top quark, which couple strongly to the Kaluza-Klein gauge bosons, the associated collider phenomenology is analyzed. In particular, we concentrate on the possible detection of the first excited state of the top, t{sup 1}, which tends to have a higher mass than the ones accessible via regular QCD production processes. We stress that the detection of these particles is still possible due to an increase in the pair production of t{sup 1} induced by the first excited state of the gluon, G{sup 1}.
119280954
Indirect probes of the MSSM after the Higgs discovery
A bstractWe study the minimal supersymmetric standard model (MSSM) with minimal flavor violation (MFV), imposing constraints from flavor physics observables and MSSM Higgs searches, in light of the recent discovery of a 125 GeV Higgs boson by ATLAS and CMS. We analyze the electroweak vacuum stability conditions to further restrict the MSSM parameter space. In addition, a connection to ultraviolet physics is shown via an implementation of renormalization group running, which determines the TeV-scale spectrum from a small set of minimal supergravity parameters. Finally, we investigate the impact from dark matter direct detection searches. Our work highlights the complementarity of collider, flavor and dark matter probes in exploring the MSSM, and shows that even in a MFV framework, flavor observables constrain the MSSM parameter space well beyond the current reach of direct SUSY particle searches.
4490264
Energy dependence of moments of net-proton multiplicity distributions at RHIC.
We report the beam energy (sqrt[sNN]=7.7-200  GeV) and collision centrality dependence of the mean (M), standard deviation (σ), skewness (S), and kurtosis (κ) of the net-proton multiplicity distributions in Au+Au collisions. The measurements are carried out by the STAR experiment at midrapidity (|y|<0.5) and within the transverse momentum range 0.4<pT<0.8  GeV/c in the first phase of the Beam Energy Scan program at the Relativistic Heavy Ion Collider. These measurements are important for understanding the quantum chromodynamic phase diagram. The products of the moments, Sσ and κσ2, are sensitive to the correlation length of the hot and dense medium created in the collisions and are related to the ratios of baryon number susceptibilities of corresponding orders. The products of moments are found to have values significantly below the Skellam expectation and close to expectations based on independent proton and antiproton production. The measurements are compared to a transport model calculation to understand the effect of acceptance and baryon number conservation and also to a hadron resonance gas model.
119232438
Study of hyperon-hyperon correlations and search for $H$-dibaryon using STAR detector at RHIC
High yield of strange particle production per central collision in nucleus-nucleus collisions at RHIC and high statistics data set from STAR experiment allow us to measure \Lambda\Lambda correlations. The \Lambda\Lambda correlation measurement is also closely related to a possible six-quark state H-dibaryon, which is yet to be observed experimentally. The first measurement of \Lambda\Lambda correlations in Au+Au collisions for \sqrt{s_{NN}}= 39, 62.4 and 200 GeV and search for H-dibaryon with its weak decay \Lambda p\pi in Au+Au collisions for \sqrt{s_{NN}}= 200 GeV using the STAR experiment at RHIC are presented here.
120977476
POLARIZATION OF RADIO PULSES FROM EXTENSIVE AIR SHOWERS.
17445573
Beam energy dependence of moments of the net-charge multiplicity distributions in Au+Au collisions at RHIC.
We report the first measurements of the moments--mean (M), variance (σ(2)), skewness (S), and kurtosis (κ)--of the net-charge multiplicity distributions at midrapidity in Au+Au collisions at seven energies, ranging from sqrt[sNN]=7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, σ(2)/M, Sσ, and κσ(2), with the expectations from Poisson and negative binomial distributions (NBDs). The Sσ values deviate from the Poisson baseline and are close to the NBD baseline, while the κσ(2) values tend to lie between the two. Within the present uncertainties, our data do not show nonmonotonic behavior as a function of collision energy. These measurements provide a valuable tool to extract the freeze-out parameters in heavy-ion collisions by comparing with theoretical models.
21999175
Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC.
Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies.