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.
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.
123105671
Radio pulses and the detection of large air showers
118405509
ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?
P. Adlarson, C. Adolph, W. Augustyniak, V. Baru, 5 M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, K.–T. Brinkmann, M. Büscher, 11 H. Calén, H. Clement, D. Coderre, 11, 12 E. Czerwiński, ∗ E. Doroshkevich, C. Ekström, R. Engels, 11 W. Erven, 11 W. Eyrich, P. Fedorets, 5 K. Föhl, K. Fransson, F. Goldenbaum, 11 P. Goslawski, K. Grigoryev, 11, 17 V. Grishina, C.–O. Gullström, J. Hampe, 11, 18 C. Hanhart, 11, 19 L. Heijkenskjöld, V. Hejny, 11 F. Hinterberger, M. Hodana, 11, 13 B. Höistad, M. Jacewicz, M. Janusz, A. Jany, B.R. Jany, L. Jarczyk, J. Jaus, T. Johansson, B. Kamys, G. Kemmerling, 11 O. Khakimova, A. Khoukaz, S. Kistryn, J. Klaja, 11, 13 H. Kleines, 11 B. Kłos, F. Kren, W. Krzemień, P. Kulessa, S. Kullander, A. Kupść, K. Lalwani, B. Lorentz, 11 A. Magiera, R. Maier, 11 P. Marciniewski, B. Mariański, M. Mikirtychiants, 11, 17 P. Moskal, H.–P. Morsch, B.K. Nandi, H. Ohm, 11 A. Passfeld, C. Pauly, 11, † E. Perez del Rio, Y. Petukhov, N. Piskunov, P. Pluciński, P. Podkopał, A. Povtoreyko, D. Prasuhn, 11 A. Pricking, 10 K. Pysz, T. Rausmann, C.F. Redmer, J. Ritman, 11, 12 A. Roy, R.J.M.Y. Ruber, Z. Rudy, S. Schadmand, 11 A. Schmidt, W. Schroeder, T. Sefzick, 11 V. Serdyuk, 11, 24 N. Shah, M. Siemaszko, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, 11 J. Stepaniak, G. Sterzenbach, 11 H. Stockhorst, 11 H. Ströher, 11 A. Szczurek, A. Täschner, T. Tolba, 11 A. Trzciński, R. Varma, P. Vlasov, G.J. Wagner, W. Węglorz, A. Winnemöller, A. Wirzba, 11, 19 M. Wolke, A. Wrońska, P. Wüstner, 11 P. Wurm, 11 L. Yurev, 11, 24 J. Zabierowski, M.J. Zieliński, W. Zipper, J. Złomańczuk, and P. Żuprański
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.
119244592
Measurement of the $pn \to pp\pi^0\pi^-$ reaction in search for the recently observed resonance structure in $d\pi^0\pi^0$ and $d\pi^+\pi^-$ systems
Exclusive measurements of the quasi-free $pn \to pp\pi^0\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2.35 - 2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, {\it i.e.} low-mass enhancement is found in the $\pi^0\pi^-$-invariant mass spectrum -- in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s-wave. At the upper end of the covered energy region $t$-channel processes for Roper, $\Delta(1600)$ and $\Delta\Delta$ excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at $m$=~2.37 GeV with $\Gamma$ =~70 MeV and $I(J^P)=~0(3^+)$ observed recently in $pn \to d\pi^0\pi^0$ and $pn \to d\pi^+\pi^-$ reactions leads to an agreement with the data also at low energies.
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.
118394634
Light Dark Matter and the Electroweak Phase Transition in the NMSSM
We analyze the stability of the vacuum and the electroweak phase transition in the NMSSM close to the Peccei-Quinn symmetry limit. This limit contains light Dark Matter (DM) particles with a mass signicantly smaller than the weak scale and also light CP-even and CP-odd Higgs bosons. Such light particles lead to a consistent relic density and facilitate a large spin-independent direct DM detection cross section, that may accommodate the recently reported signatures at the DAMA and CoGeNT experiments. Studying the one-loop eective potential at nite temperature, we show that when the lightest CP-even Higgs mass is of the order of a few GeV, the electroweak phase transition tends to become rst order and strong. The inverse relationship between the direct-detection cross-section and the lightest CP-even Higgs mass implies that a cross-section of the order of 10 41 cm 2 is correlated with a strong rst order phase transition.
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.
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}.
14413196
Gauge-Higgs Unification and Radiative Electroweak Symmetry Breaking in Warped Extra Dimensions
of large corrections to the T parameter and the coupling of the Z to the bottom quark. We demonstrate that electroweak symmetry breaking may be realized, with proper generation of the top and bottom quark masses for the same region of bulk mass parameters that lead to good agreement with precision electroweak data in the presence of a light Higgs. We compute the Higgs mass and demonstrate that for the range of parameters for which the Higgs boson has Standard Model-like properties, the Higgs mass is naturally in a range that varies between values close to the LEP experimental limit and about 160 GeV. This mass range may be probed at the Tevatron and at the LHC. We analyze the KK spectrum and briey discuss the phenomenology of the light resonances arising in our model.