81 research outputs found
Supersymmetric dark matter in the light of LEP
The negative outcome of searches for supersymmetry performed at LEP have been
used to derive indirect constraints on the parameters of the most plausible
models for cold dark matter based on supersymmetric extensions of the Standard
Model. The main results are summarized.Comment: 3 pages, 1 figure, to be published in the proceedings of the XIII
Italian meeting on Physics at LEP, LEPTRE, Rome, April 200
Dark Matter and SUSY: LEP results
The negative outcome of searches for supersymmetry performed at LEP have been
used to derive indirect constraints on the parameters of the most plausible
supersymmetric candidates for cold dark matter, in particular for the lightest
neutralino. We review the basic ideas leading to the present lower limit on the
lightest neutralino mass of about 37 GeV, with emphasis on the underlying
assumptions.Comment: 12 pages, 8 figures, to appear in the proceedings of Vulcano Workshop
2000: Frontier Objects In Astrophysics And Particle Physics, 22-27 May 2000,
Vulcano, Ital
Selected topics from non-Higgs searches at LEP
Extensive searches for new phenomena have been performed at LEP. The
principal aspects and results of those not related to Higgs bosons are reviewed
here.Comment: 4 pages, 4 figures, presented at "XXXVIIth Rencontres de Moriond on
QCD and High Energy Hadronic Interactions", Les Arcs, France, 16-23 March
200
Search for SUSY with R-parity violation at LEP
Searches for supersymmetry at LEP allowing for R-parity violation are
reviewed. The results are compared with the R-parity conserving scenarios.Comment: 8 pages, 8 figures, to be included in the proceedings of the 29th
"International Conference on High Energy Physics", Vancouver, 199
Supersymmetric Dark Matter in the Light of LEP and the Tevatron Collider
We analyze the accelerator constraints on the parameter space of the Minimal
Supersymmetric extension of the Standard Model, comparing those now available
from LEP II and anticipating the likely sensitivity of Tevatron Run II. The
most important limits are those from searches for charginos, neutralinos and
Higgs bosons at LEP, and searches for stop squarks, charginos and neutralinos
at the Tevatron Collider. We also incorporate the constraints derived from b
--> s + gamma decay, and discuss the relevance of charge- and colour-breaking
minima in the effective potential. We combine and compare the different
constraints on the Higgs-mixing parameter mu, the gaugino-mass parameter
m_{1/2} and the scalar-mass parameter m0, incorporating radiative corrections
to the physical particle masses. We focus on the resulting limitations on
supersymmetric dark matter, assumed to be the lightest neutralino,
incorporating coannihilation effects in the calculation of the relic abundance.
We find that m_chi > 51 GeV and tan(beta) > 2.2 if all soft
supersymmetry-breaking scalar masses are universal, including those of the
Higgs bosons, and that these limits weaken to m_chi > 46 GeV and tan(beta) >
1.9 if non-universal scalar masses are allowed. Light neutralino dark matter
cannot be primarily Higgsino in composition.Comment: 39 pages in LaTeX, including 44 encapsulated postscript figure
Charginos and Neutralinos in the Light of Radiative Corrections: Sealing the Fate of Higgsino Dark Matter
We analyze the LEP constraints from searches for charginos and
neutralinos , taking into account radiative corrections to the
relations between their masses and the underlying Higgs-mixing and gaugino-mass
parameters and the trilinear mass parameter . Whilst
radiative corrections do not alter the excluded domain in as a
function of , its mapping into the
plane is altered. We update our previous lower limits on the mass of gaugino
dark matter and on tan, the ratio of Higgs vacuum expectation values, in
the light of the latest LEP data and these radiative corrections. We also
discuss the viability of Higgsino dark matter, incorporating co-annihilation
effects into the calculation of the Higgsino relic abundance. We find that
Higgsino dark matter is viable for only a very limited range of and
, which will be explored completely by upcoming LEP runs.Comment: Version to appear in Phys. Rev. D., 21 pages in LateX, including 10
encapsulated postscript figures; uses epsf.sty.; Figures modified (one
deleted), conclusions unchange
The Need for a Versioned Data Analysis Software Environment
Scientific results in high-energy physics and in many other fields often rely
on complex software stacks. In order to support reproducibility and scrutiny of
the results, it is good practice to use open source software and to cite
software packages and versions. With ever-growing complexity of scientific
software on one side and with IT life-cycles of only a few years on the other
side, however, it turns out that despite source code availability the setup and
the validation of a minimal usable analysis environment can easily become
prohibitively expensive. We argue that there is a substantial gap between
merely having access to versioned source code and the ability to create a data
analysis runtime environment. In order to preserve all the different variants
of the data analysis runtime environment, we developed a snapshotting file
system optimized for software distribution. We report on our experience in
preserving the analysis environment for high-energy physics such as the
software landscape used to discover the Higgs boson at the Large Hadron
Collider
Supersymmetric Dark Matter and the Energy of a Linear Electron-Positron Collider
We suggest that supersymmetric dark matter be used to set the energy scale of a linear collider. Assuming that the lightest supersymmetric particle (LSP) is a stable neutralino , as in many incarnations of the MSSM with conserved R parity, previous calculations that include coannihilation effects have delineated the region of the plane where the LSP cosmological relic density lies in the preferred range 0.1 \la \Omega_{\chi} h^2 \la 0.3. We evaluate here the total cross section for visible pairs of supersymmetric particles, for different values of and , and investigate how much of the dark matter region can be explored by colliders with different centre-of-mass energies . We find that a collider with GeV or 1 TeV can only explore part of the cosmological region, and that a collider with TeV with sufficient luminosity can explore all of the supersymmetric dark matter region
PROOF as a Service on the Cloud: a Virtual Analysis Facility based on the CernVM ecosystem
PROOF, the Parallel ROOT Facility, is a ROOT-based framework which enables
interactive parallelism for event-based tasks on a cluster of computing nodes.
Although PROOF can be used simply from within a ROOT session with no additional
requirements, deploying and configuring a PROOF cluster used to be not as
straightforward. Recently great efforts have been spent to make the
provisioning of generic PROOF analysis facilities with zero configuration, with
the added advantages of positively affecting both stability and scalability,
making the deployment operations feasible even for the end user. Since a
growing amount of large-scale computing resources are nowadays made available
by Cloud providers in a virtualized form, we have developed the Virtual
PROOF-based Analysis Facility: a cluster appliance combining the solid CernVM
ecosystem and PoD (PROOF on Demand), ready to be deployed on the Cloud and
leveraging some peculiar Cloud features such as elasticity. We will show how
this approach is effective both for sysadmins, who will have little or no
configuration to do to run it on their Clouds, and for the end users, who are
ultimately in full control of their PROOF cluster and can even easily restart
it by themselves in the unfortunate event of a major failure. We will also show
how elasticity leads to a more optimal and uniform usage of Cloud resources.Comment: Talk from Computing in High Energy and Nuclear Physics 2013
(CHEP2013), Amsterdam (NL), October 2013, 7 pages, 4 figure
ROOT - A C++ Framework for Petabyte Data Storage, Statistical Analysis and Visualization
ROOT is an object-oriented C++ framework conceived in the high-energy physics
(HEP) community, designed for storing and analyzing petabytes of data in an
efficient way. Any instance of a C++ class can be stored into a ROOT file in a
machine-independent compressed binary format. In ROOT the TTree object
container is optimized for statistical data analysis over very large data sets
by using vertical data storage techniques. These containers can span a large
number of files on local disks, the web, or a number of different shared file
systems. In order to analyze this data, the user can chose out of a wide set of
mathematical and statistical functions, including linear algebra classes,
numerical algorithms such as integration and minimization, and various methods
for performing regression analysis (fitting). In particular, ROOT offers
packages for complex data modeling and fitting, as well as multivariate
classification based on machine learning techniques. A central piece in these
analysis tools are the histogram classes which provide binning of one- and
multi-dimensional data. Results can be saved in high-quality graphical formats
like Postscript and PDF or in bitmap formats like JPG or GIF. The result can
also be stored into ROOT macros that allow a full recreation and rework of the
graphics. Users typically create their analysis macros step by step, making use
of the interactive C++ interpreter CINT, while running over small data samples.
Once the development is finished, they can run these macros at full compiled
speed over large data sets, using on-the-fly compilation, or by creating a
stand-alone batch program. Finally, if processing farms are available, the user
can reduce the execution time of intrinsically parallel tasks - e.g. data
mining in HEP - by using PROOF, which will take care of optimally distributing
the work over the available resources in a transparent way
- …