891 research outputs found
Effect on the electron EDM due to abelian gauginos in SUSY extra U(1) models
The electric dipole moment of an electron (EDME) is investigated in the
supersymmetric extra U(1) models. Neutralino sector is generally extended in
these models and then the neutralino contribution will be important for the
analysis of the EDME. Kinetic term mixings of abelian gauginos are taken into
account in our analysis. Numerical results for the extra U(1) models show that
the EDME can be affected by the extra U(1) in a certain range of soft
supersymmetry breaking parameters even if the extra U(1) gauge boson is heavy.
The EDME may be a clue to find an extended gauge structure in the
supersymmetric models.Comment: 16 pages, latex, 3 figure
Spin Physics at e^+e^- Colliders
A large number of measurements with polarized beams and/or spin analysis of
final state particles has been performed at the e^+e^- colliders LEP and SLC,
providing important information on the dynamics of high energy interactions. In
this paper three subjects, for which the role of spin studies was particularly
relevant, will be covered: the measurements of the electroweak couplings, the
study of fragmentation dynamics and the search for physics beyond the Standard
Model.Comment: 11 pages, Invited talk given at the International Workshop on
Symmetry and Spin - Prague, Czech Republic, August 30 - September 5, 199
Year in review 2008: Critical Care - sepsis
The present report highlights the most important papers appearing in Critical Care and other major journals about severe sepsis, the systemic inflammatory response and multiorgan dysfunction over the past year. A number of these clinical and laboratory studies will have a considerable impact on the sepsis research agenda for years to come. The steroid controversy, the debate over tight glycemic control, the colloid versus crystalloid issue, the value of selective decontamination of the digestive tract, the enlarging role of biomarkers, the value of genomics and rapid diagnostic techniques have all been prominently featured in recent publications. Basic research into novel predictive assays, genetic polymorphisms, and new molecular methods to risk-stratify and to determine treatment options for sepsis have occupied much of the Critical Care publications relating to sepsis pathophysiology in 2008. We will attempt to briefly summarize what we consider to be the most significant contributions to the sepsis literature over the last year, and their likely ramifications in the future, for critical care clinicians, clinical investigators and basic researchers alike
Forward-backward multiplicity correlations and leakage parameter behaviour in asymmetric high energy collisions
Continuing previous work, forward-backward multiplicity correlations are
studied in asymmetric collisions in the framework of the weighted superposition
mechanism of different classes of events. New parameters for the asymmetric
clan distribution and for the particle leakage from clans in one hemisphere to
the opposite one are introduced to effectively classify different classes of
collisions. This tool should be used to explore forward-backward multiplicity
correlations in AB and pA collisions in present and future experiments at RHIC
and LHC.Comment: 14 pages, 2 figures, latex 2e with amsmat
Unanswered Questions in the Electroweak Theory
This article is devoted to the status of the electroweak theory on the eve of
experimentation at CERN's Large Hadron Collider. A compact summary of the logic
and structure of the electroweak theory precedes an examination of what
experimental tests have established so far. The outstanding unconfirmed
prediction of the electroweak theory is the existence of the Higgs boson, a
weakly interacting spin-zero particle that is the agent of electroweak symmetry
breaking, the giver of mass to the weak gauge bosons, the quarks, and the
leptons. General arguments imply that the Higgs boson or other new physics is
required on the TeV energy scale. Indirect constraints from global analyses of
electroweak measurements suggest that the mass of the standard-model Higgs
boson is less than 200 GeV. Once its mass is assumed, the properties of the
Higgs boson follow from the electroweak theory, and these inform the search for
the Higgs boson. Alternative mechanisms for electroweak symmetry breaking are
reviewed, and the importance of electroweak symmetry breaking is illuminated by
considering a world without a specific mechanism to hide the electroweak
symmetry.
For all its triumphs, the electroweak theory has many shortcomings. . . .Comment: 31 pages, 20 figures; prepared for Annual Review of Nuclear and
Particle Science (minor changes
Production of Triply Charmed Baryons in Annihilation
The total and differential cross sections for the production of triply
charmed baryons in annihilation are calculated at
the -boson pole.Comment: 13 pages, 2 figure
Uncertainties of the CJK 5 Flavour LO Parton Distributions in the Real Photon
Radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real,
unpolarized photon, calculated in the CJK model being an improved realization
of the CJKL approach, have been recently presented. The results were obtained
through a global fit to the experimental F2^gamma data. In this paper we
present, obtained for the very first time in the photon case, an estimate of
the uncertainties of the CJK parton distributions due to the experimental
errors. The analysis is based on the Hessian method which was recently applied
in the proton parton structure analysis. Sets of test parametrizations are
given for the CJK model. They allow for calculation of its best fit parton
distributions along with F2^gamma and for computation of uncertainties of any
physical value depending on the real photon parton densities. We test the
applicability of the approach by comparing uncertainties of example
cross-sections calculated in the Hessian and Lagrange methods. Moreover, we
present a detailed analysis of the chi^2 of the CJK fit and its relation to the
data. We show that large chi^2/DOF of the fit is due to only a few of the
experimental measurements. By excluding them chi^2/DOF approx 1 can be
obtained.Comment: 28 pages, 8 eps figures, 2 Latex figures; FORTRAN programs available
at http://www.fuw.edu.pl/~pjank/param.html; table 10, figure 10 and section 6
correcte
The MSSM fine tuning problem: a way out
As is well known, electroweak breaking in the MSSM requires substantial
fine-tuning, mainly due to the smallness of the tree-level Higgs quartic
coupling, lambda_tree. Hence the fine tuning is efficiently reduced in
supersymmetric models with larger lambda_tree, as happens naturally when the
breaking of SUSY occurs at a low scale (not far from the TeV). We show, in
general and with specific examples, that a dramatic improvement of the fine
tuning (so that there is virtually no fine-tuning) is indeed a very common
feature of these scenarios for wide ranges of tan(beta) and the Higgs mass
(which can be as large as several hundred GeV if desired, but this is not
necessary). The supersymmetric flavour problems are also drastically improved
due to the absence of RG cross-talk between soft mass parameters.Comment: 28 pages, 9 PS figures, LaTeX Published versio
Copy Number Variants Are Ovarian Cancer Risk Alleles at Known and Novel Risk Loci
Background Known risk alleles for epithelial ovarian cancer (EOC) account for approximately 40% of the heritability for EOC. Copy number variants (CNVs) have not been investigated as EOC risk alleles in a large population cohort. Methods Single nucleotide polymorphism array data from 13 071 EOC cases and 17 306 controls of White European ancestry were used to identify CNVs associated with EOC risk using a rare admixture maximum likelihood test for gene burden and a by-probe ratio test. We performed enrichment analysis of CNVs at known EOC risk loci and functional biofeatures in ovarian cancer-related cell types. Results We identified statistically significant risk associations with CNVs at known EOC risk genes; BRCA1 (P-EOC = 1.60E-21; OREOC = 8.24), RAD51C (Phigh-grade serous ovarian cancer [HGSOC] = 5.5E-4; odds ratio [OR](HGSOC) = 5.74 del), and BRCA2 (P-HGSOC = 7.0E-4; ORHGSOC = 3.31 deletion). Four suggestive associations (P < .001) were identified for rare CNVs. Risk-associated CNVs were enriched (P < .05) at known EOC risk loci identified by genome-wide association study. Noncoding CNVs were enriched in active promoters and insulators in EOC-related cell types. Conclusions CNVs in BRCA1 have been previously reported in smaller studies, but their observed frequency in this large population-based cohort, along with the CNVs observed at BRCA2 and RAD51C gene loci in EOC cases, suggests that these CNVs are potentially pathogenic and may contribute to the spectrum of disease-causing mutations in these genes. CNVs are likely to occur in a wider set of susceptibility regions, with potential implications for clinical genetic testing and disease prevention.Peer reviewe
Questions and Remarks About Clans in Multiparticle Dynamics
The fact that several important effects in multiparticle dynamics, on which
QCD has not yet satisfactory predictions, have been interpreted in terms of the
validity of negative binomial (Pascal) regularity and related clan properties
at the level of simpler substructures, raises intriguing questions on clan
properties in all classes of collisions, the main one being whether clans are
observable objects or merely a mathematical concept. We approach this problem
by studying clan masses and rapidity distributions in each substructure for
e+e- annihilation and hh collisions, and find that such properties can indeed
characterise the different components. These results support the idea that
clans could be observable, a challenging problem for future experiments.Comment: 11 pages; 3 figures; latex 2e and amsmat
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