Determination of MSSM Parameters from LHC and ILC Observables in a Global Fit

We present the results of a realistic global fit of the Lagrangian parameters of the Minimal Supersymmetric Standard Model assuming universality for the first and second generation and real parameters. No assumptions on the SUSY breaking mechanism are made. The fit is performed using the precision of future mass measurements of superpartners at the LHC and mass and polarized topological cross-section measurements at the ILC. Higher order radiative corrections are accounted for whereever possible to date. Results are obtained for a modified SPS1a MSSM benchmark scenario but they were checked not to depend critically on this assumption. Exploiting a simulated annealing algorithm, a stable result is obtained without any a priori assumptions on the values of the fit parameters. Most of the Lagrangian parameters can be extracted at the percent level or better if theoretical uncertainties are neglected. Neither LHC nor ILC measurements alone will be sufficient to obtain a stable result. The effects of theoretical uncertainties arising from unknown higher-order corrections and parametric uncertainties are examined qualitatively. They appear to be relevant and the result motivates further precision calculations. The obtained parameters at the electroweak scale are used for a fit of the parameters at high energy scales within the bottom-up approach. In this way regularities at these scales are explored and the underlying model can be determined with hardly any theoretical bias. Fits of high-scale parameters to combined LHC+ILC measurements within the mSUGRA framework reveal that even tiny distortions in the low-energy mass spectrum already lead to inacceptable chi^2 values. This does not hold for ``LHC only'' inputs.Comment: 25 pages, 5 figure

Two-pion Bose-Einstein correlations in central Pb-Pb collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV

The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV at the Large Hadron Collider is presented. We observe a growing trend with energy now not only for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/388

Masses and couplings of vector mesons from the pion electromagnetic, weak, and \pi\gamma transition form factors

We analyse the pion electromagnetic, charged-current, and $\pi\gamma$ transition form factors at timelike momentum transfers $q$, $q^2=s\le 1.4$ GeV$^2$, using a dispersion approach. We discuss in detail the propagator matrix of the photon-vector-meson system and define certain reduced amplitudes, or vertex functions, describing the coupling of this system to final states. We then apply the derived analytic expressions to the analysis of the recent $e^+e^-\to \pi^+\pi^-$, $\tau^-\to \pi^-\pi^0\nu_\tau$, and $e^+e^-\to \pi^0\gamma$ data. We find the reduced amplitudes for the coupling of the photon and vector mesons to two pseudoscalars to be constant, independent of $s$, in the range considered, indicating a "freezing" of the amplitudes for $s\le 1$ GeV. The fit to the form factor data leads to the following values of the Breit-Wigner resonance masses m_{\rho^-}=775.3\pm 0.8 MeV, m_{\rho^0}=773.7\pm 0.6 MeV and m_\omega=782.43\pm 0.05 MeV, where the errors are only statistical.Comment: revtex, 23 page

Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}} = 2.76 TeV

Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in $|\eta|<0.8$ and $0.3 < p_T < 20$ GeV/$c$ are compared to the expectation in pp collisions at the same $\sqrt{s_{\rm NN}}$, scaled by the number of underlying nucleon-nucleon collisions. The comparison is expressed in terms of the nuclear modification factor $R_{\rm AA}$. The result indicates only weak medium effects ($R_{\rm AA} \approx$ 0.7) in peripheral collisions. In central collisions, $R_{\rm AA}$ reaches a minimum of about 0.14 at $p_{\rm T}=6$-7GeV/$c$ and increases significantly at larger $p_{\rm T}$. The measured suppression of high-$p_{\rm T}$ particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb-Pb collisions at the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98

Probing dense and hot matter with low-mass dileptons and photons

Results on low-mass dileptons, covering the very broad energy range from the BEVALAC up to SPS are reviewed. The emphasis is on the open questions raised by the intriguing results obtained so far and the prospects for addressing them in the near future with the second generation of experiments, in particular HADES, NA60 and PHENIX.Comment: 6 pages, 8 figures, Proceedings of Hard Probes 2004 Conference, Ericeira, November 4-10, 2004. Caption of Figure 2 corrected. To be published in Eur. Phys. J. C. The orginal version is available at www.springerlink.co

Do we understand the single-spin asymmetry for pi0pi^0 inclusive production in pp collisions?

The cross section data for $\pi^0$ inclusive production in $pp$ collisions is considered in a rather broad kinematic region in energy $\sqrt{s}$, Feynman variable $x_F$ and transverse momentum $p_T$. The analysis of these data is done in the perturbative QCD framework at the next-to-leading order. We find that they cannot be correctly described in the entire kinematic domain and this leads us to conclude that the single-spin asymmetry, $A_N$ for this process, observed several years ago at FNAL by the experiment E704 and the recent result obtained at BNL-RHIC by STAR, are two different phenomena. This suggests that STAR data probes a genuine leading-twist QCD single-spin asymmetry for the first time and finds a large effect.Comment: text modified, version to be published in Eur. Phys. J. C, 6 pages, 5 figure

First-Year Papers Cover Page and Editorial Board

Volume 17, 2012 – 2013 EDITORS First-Year Program Margaret Lindsey, Dean Erin Valentino, Research Education Librarian Dania Field, Program Assistant First-Year Mentors Andrew Bannon-Guasp ‘13 Elizabeth Preysner ‘13 Megan Baxter ‘13 Junius Ross-Martin ‘15 Emma Belloumo ‘13 Lillian Young ‘13 Elizabeth Bilfinger ’13 Abigail Whalen ‘15 Editing, Layout, and Publishing Dania Field Amy Harrell Elizabeth Preysner The First-Year Papers were established in 1996-1997 to recognize the excellent written work of the first-year students at Trinity College. Each year, submissions are drawn from First-Year Seminars and from courses associated with the Cities, Guided Studies, InterArts, and Interdisciplinary Science Programs. The First-Year Papers Volume 17, 2012 – 2013 Published by Trinity College Hartford, Connecticut, September 201