116 research outputs found
One-loop MSSM Contribution to the Weak Magnetic Dipole Moments of Heavy Fermions
The MSSM predictions at the one-loop level for the weak-magnetic dipole
moments of the lepton and the quark are analysed. The entire
supersymmetric parameter space is scannedwith the usual GUT constraint and
common squark and slepton mass parameters. The real part of is
dominated by the chargino contribution, being the same order as the SM one or
even larger in the high region whereas the imaginary part, due to
Higgs boson diagrams, is negligible comparedto the SM value. The real part
of is controlled mainly by charginos andalso by gluinos, when the mixing
in the bottom squark sector is large, to yield, for high , a
contribution one order of magnitude largerthan the pure electroweak SM value
but a factor five smaller than the standard QCD contribution. The imaginary
part of is the same order as in the SM.Comment: 14 pages, Latex, 4 eps and 1 ps figure, needs epsfig.sty. Minor
changes, new references added. To be published in Phys. Lett.
Status of the Fermilab Muon (g-2) Experiment
The New Muon Collaboration at Fermilab has proposed to measure the
anomalous magnetic moment of the muon, , a factor of four better than
was done in E821 at the Brookhaven AGS, which obtained ppm. The last digit of is changed
from the published value owing to a new value of the ratio of the
muon-to-proton magnetic moment that has become available. At present there
appears to be a difference between the Standard-Model value and the measured
value, at the standard deviation level when electron-positron
annihilation data are used to determine the lowest-order hadronic piece of the
Standard Model contribution. The improved experiment, along with further
advances in the determination of the hadronic contribution, should clarify this
difference. Because of its ability to constrain the interpretation of
discoveries made at the LHC, the improved measurement will be of significant
value, whatever discoveries may come from the LHC.Comment: Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, China, 4
pages 2 figures. Version 2 includes Fermilab report number, minor corrections
and one additional referenc
Precision Observables in the MSSM: W mass and the muon magnetic moment
The precision observables M_W and g-2 of the muon are discussed in the
framework of the MSSM. Recent progress in the evaluation of the theoretical
predictions is described, and the MSSM predictions are compared with the SM
predictions and the experimental values.Comment: 4 pages, 2 figures. To appear in Proceedings of SUSY06, the 14th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions, UC Irvine, California, 12-17 June 200
Dipole Form Factors and Loop-induced CP-violation in Supersymmetry
The one-loop Minimal Supersymmetric Standard Model (MSSM) contributions to
the weak and electromagnetic dipole form factors of heavy fermions are
reviewed. For the boson on shell, the weak-magnetic and weak-electric
dipole moments of the lepton and the quark can be defined and
directly connected to observables. But far from the peak, the weak and
electromagnetic dipole form factors are not enough to account for all the new
physics effects. In the context of the calculation of the process to one loop in the MSSM, we compare the impact on the phenomenology
of the CP-violating dipole form factors of the top quark with the contribution
from CP-violating box graphs. Some exemplificative observables are analyzed and
the relevance of both the contributions is pointed out. The set of tensor
integrals employed, the one-loop expressions for the electromagnetic and weak
dipole form factors in a general renormalizable theory and the SM and MSSM
couplings and conventions are also given.Comment: 68 pages, 17 figures. LaTeX using epsf.sty. Eqs. (61,66,67)
corrected. Labels `N' and `T' exchanged in Tables 5,6. Tables 6,7 and Figure
15 revise
橘の花散る里のほととぎす--「万葉集」巻8,1472,1473番歌をめぐって
R-symmetry leads to a distinct low energy realisation of SUSY with a signicantly modified colour-charged sector featuring a Dirac gluino and scalar colour octets (sgluons). In the present work we recast results from LHC BSM searches to discuss the impact of R-symmetry on the squark and gluino mass limits. We work in the framework of the Minimal R-symmetric Supersymmetric Standard Model and take into account the NLO corrections to the squark production cross sections in the MRSSM that have become available recently. We find substantially weaker limits on squark masses compared to the MSSM: for simple scenarios with heavy gluinos and degenerate squarks, the MRSSM mass limit is > 1:7TeV, approximately 600 GeV lower than in the MSSM
Gyromagnetic Ratio of Charged Kerr-Anti-de Sitter Black Holes
We examine the gyromagnetic ratios of rotating and charged AdS black holes in
four and higher spacetime dimensions. We compute the gyromagnetic ratio for
Kerr-AdS black holes with an arbitrary electric charge in four dimensions and
show that it corresponds to g=2 irrespective of the AdS nature of the
spacetime. We also compute the gyromagnetic ratio for Kerr-AdS black holes with
a single angular momentum and with a test electric charge in all higher
dimensions. The gyromagnetic ratio crucially depends on the dimensionless ratio
of the rotation parameter to the curvature radius of the AdS background. At the
critical limit, when the boundary Einstein universe is rotating at the speed of
light, it exhibits a striking feature leading to g=2 regardless of the
spacetime dimension. Next, we extend our consideration to include the exact
metric for five-dimensional rotating charged black holes in minimal gauged
supergravity. We show that the value of the gyromagnetic ratio found in the
"test-charge" approach remains unchanged for these black holes.Comment: New section added; 6 pages, RevTe
Charm Quark Contribution to K+ -> pi+ nu anti-nu at Next-to-Next-to-Leading Order
We calculate the complete NNLO QCD corrections to the charm contribution of
the rare decay K+ -> pi+ nu nu-bar. We encounter several new features, which
were absent in lower orders. We discuss them in detail and present the results
for the 2-loop matching conditions of the Wilson coefficients, the 3-loop
anomalous dimensions, and the 2-loop matrix elements of the relevant operators
that enter the NNLO renormalization group analysis of the Z-penguin and the
electroweak box contribution. The inclusion of the NNLO QCD corrections leads
to a significant reduction of the theoretical uncertainty from 9.8% down to
2.4% in the relevant parameter Pc, implying the leftover scale uncertainties in
BR(K+ -> pi+ nu nu-bar) and in the determination of |V_td|, sin(2 beta), and
gamma from the K -> pi nu nu system to be 1.3%, 1.0%, 0.006, and 1.2 degrees,
respectively. For the charm quark MSbar mass mc=(1.30+-0.05) GeV and |V_us|=
0.2248 the NLO value Pc=0.37+-0.06 is modified to Pc=0.38+-0.04 at the NNLO
level with the latter error fully dominated by the uncertainty in mc. We
present tables for Pc as a function of mc and alphas(MZ) and a very accurate
analytic formula that summarizes these two dependences as well as the dominant
theoretical uncertainties. Adding the recently calculated long-distance
contributions we find BR(K+ -> pi+ nu nu-bar)=(8.0+-1.1)*10^-11 with the
present uncertainties in mc and the Cabibbo-Kobayashi-Maskawa elements being
the dominant individual sources in the quoted error. We also emphasize that
improved calculations of the long-distance contributions to K+ -> pi+ nu nu-bar
and of the isospin breaking corrections in the evaluation of the weak current
matrix elements from K+ -> pi0 e+ nu would be valuable in order to increase the
potential of the two golden K -> pi nu nu decays in the search for new physics.Comment: 74 pages, 28 figures. Erratum added: We correct the treatment of
anomalous triangle diagrams. The associated numerical correction is below a
permille; v3: Typographical mistakes in (108), (111) and (112) corrected.
Thanks to Xu Feng for pointing them out. Numerical results unchange
Single top-quark production by strong and electroweak supersymmetric flavor-changing interactions at the LHC
(Abridged) We report on a complete study of the single top-quark production
by direct supersymmetric flavor-changing neutral-current (FCNC) processes at
the LHC. The total cross section for pp(gg)->t\bar{c}+\bar{t}c is computed at
the 1-loop order within the unconstrained Minimal Supersymmetric Standard Model
(MSSM). The present study extends the results of the supersymmetric strong
effects (SUSY-QCD), which were advanced by some of us in a previous work, and
includes the computation of the full supersymmetric electroweak corrections
(SUSY-EW). Our analysis of pp(gg)->t\bar{c}+\bar{t}c in the MSSM has been
performed in correspondence with the stringent low-energy constraints from b->s
gamma. In the most favorable scenarios, the SUSY-QCD contribution can give rise
to production rates of around 10^5 events per 100 fb^{-1} of integrated
luminosity. Furthermore, we show that there exist regions of the MSSM parameter
space where the SUSY-EW correction becomes sizeable. In the SUSY-EW favored
regions, one obtains lower, but still appreciable, event production rates that
can reach the 10^3 level for the same range of integrated luminosity. We study
also the possible reduction in the maximum event rate obtained from the full
MSSM contribution if we additionally include the constraints from
B^0_s-\bar{B}^0_s. In view of the fact that the FCNC production of heavy quark
pairs of different flavors is extremely suppressed in the SM, the detection of
a significant number of these events could lead to evidence of new physics --
of likely supersymmetric origin.Comment: LaTex, 35 pages, typos corrected. Version accepted in JHE
Searching for physics beyond the Standard Model through the dipole interaction
The magnetic dipole interaction played a central role in the development of
QED, and continued in that role for the Standard Model. The muon anomalous
magnetic moment has served as a benchmark for models of new physics, and the
present experimental value is larger than the standard-model value by more than
three standard deviations. The electric dipole moment (EDM) violates parity
({}) and time-reversal ({}) symmetries, and in the context of the
theorem, the combination of charge conjugation and parity (). Since a new
source of {} violation outside of that observed in the and meson
systems is needed to help explain the baryon asymmetry of the universe,
searches for EDMs are being carried out worldwide on a number of systems. The
standard-model value of the EDM is immeasurably small, so any evidence for an
EDM would signify the observation of new physics. Unique opportunities exist
for EDM searches using polarized proton, deuteron or muon beams in storage
rings. This talk will provide an overview of the theory of dipole moments, and
the relevant experiments. The connection to the transition dipole moment that
could produce lepton flavor violating interactions such as is also mentioned.Comment: Invited Plenary talk at the 19th International Spin Physics
Symposium, Juelic
To , or not to : Recent developments and comparisons of regularization schemes
We give an introduction to several regularization schemes that deal with
ultraviolet and infrared singularities appearing in higher-order computations
in quantum field theories. Comparing the computation of simple quantities in
the various schemes, we point out similarities and differences between them.Comment: 61 pages, 12 figures; version sent to EPJC, references update
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