18,883,136 research outputs found
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 = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at 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
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 inclusive production in pp collisions?
The cross section data for inclusive production in collisions is
considered in a rather broad kinematic region in energy , Feynman
variable and transverse momentum . 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, 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
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
transition form factors at timelike momentum transfers ,
GeV, 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
, , and data. We find the reduced amplitudes for the coupling of the
photon and vector mesons to two pseudoscalars to be constant, independent of
, in the range considered, indicating a "freezing" of the amplitudes for
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 TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 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 and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- 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
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
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