118570168
SUSY-Breaking Parameters from RG Invariants at the LHC
We study Renormalization Group invariant (RGI) quantities in the Minimal Supersymmetric Standard Model and show that they are a powerful and simple instrument for testing high scale models of supersymmetry (SUSY)-breaking. For illustration, we analyze the frameworks of minimal and general gauge mediated (MGM and GGM) SUSY-breaking, with additional arbitrary soft Higgs mass parameters at the messenger scale. We show that if a gaugino and two first generation sfermion soft masses are determined at the LHC, the RGIs lead to MGM sum rules that yield accurate predictions for the other gaugino and first generation soft masses. RGIs can also be used to reconstruct the fundamental MGM parameters (including the messenger scale), calculate the hypercharge D-term, and find relationships among the third generation and Higgs soft masses. We then study the extent to which measurements of the full first generation spectrum at the LHC may distinguish different SUSY-breaking scenarios. In the case of MGM, although most deviations violate the sum rules by more than estimated experimental errors, we find a 1-parameter family of GGM models that satisfy the constraints and produce the same first generation spectrum. The GGM-MGM degeneracy is lifted by differences in the third generation masses and the messenger scales. ∗http://theory.fnal.gov ar X iv :1 01 1. 49 58 v2 [ he pph ] 1 0 M ar 2 01 1
118375808
Determining the structure of supersymmetry breaking with renormalization group invariants
If collider experiments demonstrate that the minimal supersymmetric standard model (MSSM) is a good description of nature at the weak scale, the experimental priority will be the precise determination of superpartner masses. These masses are governed by the weak scale values of the soft supersymmetry-breaking (SUSY-breaking) parameters, which are in turn highly dependent on the SUSY-breaking scheme present at high scales. It is therefore of great interest to find patterns in the soft parameters that can distinguish different high-scale SUSY-breaking structures, identify the scale at which the breaking is communicated to the visible sector, and determine the soft breaking parameters at that scale. In this work, we demonstrate that 1-loop renormalization group invariant quantities present in the MSSM may be used to answer each of these questions. We apply our method first to generic flavor-blind models of SUSY breaking, and then we examine in detail the subset of these models described by general gauge mediation and the constrained MSSM with nonuniversal Higgs masses. As renormalization group invariance generally does not hold beyond leading-log order, we investigate the magnitude and direction of the 2-loop corrections. We find that with superpartners at the TeV scale, these 2-loop effects are either negligible, ormore » they are of the order of optimistic experimental uncertainties and have definite signs, which allows them to be easily accounted for in the overall uncertainty.« less
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.
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.
56430796
Measurements of $D^{0}$ and $D^{*}$ Production in $p$ + $p$ Collisions at $\sqrt{s}$ = 200 GeV
We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$, $D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $d\sigma/dy|_{y=0}^{c\bar{c}}$ = 170 $\pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $\mu$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.
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.
119024805
Femtoscopy of identified particles at STAR
Abstract We present new measurements of Λ – Λ correlations, which are closely related to the H -dibaryon: a six quark state predicted by Jaffe [R. Jaffe, Phys. Rev. Lett. 38 (1977) 195], in Au + Au collisions at s N N = 200 GeV from the STAR experiment. Fits to different potential models are discussed and the extracted scattering length and effective range are also presented. We also present a spherical harmonic decomposition of the pion-kaon correlation function for 0–5% centrality in Au + Au collisions at s N N = 200 GeV . Finally, we discuss results from azimuthal HBT for collision energies in the range 7.7–200 GeV.
27276714
Precision Measurement of the Longitudinal Double-Spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at sqrt[s]=200  GeV.
We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_{LL}, in polarized pp collisions at center-of-mass energy sqrt[s]=200  GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x>0.05.
3067087
Observation of an energy-dependent difference in elliptic flow between particles and antiparticles in relativistic heavy ion collisions.
Elliptic flow (v(2)) values for identified particles at midrapidity in Au + Au collisions, measured by the STAR experiment in the beam energy scan at RHIC at sqrt[s(NN)] = 7.7-62.4 GeV, are presented. A beam-energy-dependent difference of the values of v(2) between particles and corresponding antiparticles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and antiparticles are not consistent with the universal number-of-constituent-quark scaling of v(2) that was observed at sqrt[s(NN)] = 200 GeV.