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.
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
14783506
System-size dependence of transverse momentum correlations at √s NN=62.4 and 200 GeV at the BNL Relativistic Heavy Ion Collider
We present a study of the average transverse momentum ($p_t$) fluctuations and $p_t$ correlations for charged particles produced in Cu+Cu collisions at midrapidity for $\sqrt{s_{NN}} =$ 62.4 and 200 GeV. These results are compared with those published for Au+Au collisions at the same energies, to explore the system size dependence. In addition to the collision energy and system size dependence, the $p_t$ correlation results have been studied as functions of the collision centralities, the ranges in $p_t$, the pseudorapidity $\eta$, and the azimuthal angle $\phi$. The square root of the measured $p_t$ correlations when scaled by mean $p_t$ is found to be independent of both colliding beam energy and system size studied. Transport-based model calculations are found to have a better quantitative agreement with the measurements compared to models which incorporate only jetlike correlations.
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.
5210769
Braneworld graviton interactions in early universe phase transitions
This chapter discusses the Braneworld models that solve the hierarchy problem. The chapter focuses on Randall-Sundrum (RS) type models that embed one or two branes into a five dimensional AdS bulk. In RS 1, a static solution of the 5d Einstein equations is derived with two branes of opposite tension at the orbifold fixed points of the finite fifth dimension. Low-scale gravity leads to low reheating temperatures, and it is possible to obtain temperatures lower than the electroweak scale. This implies that the electroweak phase transition can take place before the completion of reheating. The chapter discusses how the gravitons couple in order to matter fields on the brane. The KK decomposition, graviton propagators and their coupling to matter and gauge fields are considered for toroidal extra dimensions and the analysis for the infinite AdS bulks have to be repeated.
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.
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.
15534390
Gravitons and dark matter in universal extra dimensions
Models of universal extra dimensions (UED) at the TeV scale lead to the presence of Kaluza Klein (KK) excitations of the ordinary fermions and bosons of the standard model that may be observed at hadron and lepton colliders. A conserved discrete symmetry, KK-parity, ensures the stability of the lightest KK particle (LKP), which, if neutral, becomes a good dark matter particle. It has been recently shown that for a certain range of masses of the LKP a relic density consistent with the experimentally observed one may be obtained. These works, however, ignore the impact of KK graviton production at early times. Whether the G{sup 1} is the LKP or not, the G{sup n} tower thus produced can decay to the LKP, and depending on the reheating temperature, may lead to a modification of the relic density. In this article, we show that this effect may lead to a relevant modification of the range of KK masses consistent with the observed relic density. Additionally, if evidence for UED is observed experimentally, we find a stringent upper limit on the reheating temperature depending on the mass of the LKP observed.
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}.