1,334 research outputs found
Supersymmetric virtual effects in heavy quark pair production at LHC
We consider the production of heavy () quark pairs at proton colliders
in the theoretical framework of the MSSM. Under the assumption of a
"moderately" light SUSY scenario, we first compute the leading logarithmic MSSM
contributions at one loop for the elementary processes of production from a
quark and from a gluon pair in the 1 TeV c.m. energy region. We show that in
the initial gluon pair case (dominant in the chosen situation at LHC energies)
the electroweak and the strong SUSY contributions concur to produce an enhanced
effect whose relative value in the cross sections could reach the twenty
percent size for large values in the realistic proton-proton LHC
process.Comment: 19 pages and 8 figures; version to appear in Phys. Rev.
Charged Higgs Production in the 1 TeV Domain as a Probe of Supersymmetric Models
We consider the production, at future lepton colliders, of charged Higgs
pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and
working in the MSSM, we show that, for c.m. energies in the one TeV range, a
one-loop logarithmic Sudakov expansion that includes an "effective" next-to
subleading order term is adequate to the expected level of experimental
accuracy. We consider then the coefficient of the linear (subleading) SUSY
Sudakov logarithm and the SUSY next to subleading term of the expansion and
show that their dependence on the supersymmetric parameters of the model is
drastically different. In particular the coefficient of the SUSY logarithm is
only dependent on while the next to subleading term depends on a
larger set of SUSY parameters. This would allow to extract from the data
separate informations and tests of the model.Comment: 18 pages and 13 figures e-mail: [email protected]
Reliability of a high energy one-loop expansion of e+e- --> W+W- in the SM and in the MSSM
We compare the logarithmic Sudakov expansions of the process e+e- --> W+W- in
the one-loop approximation and in the resummed version, to subleading order
accuracy, in the SM case and in a light SUSY scenario for the MSSM. We show
that the two expansions are essentially identical below 1 TeV, but differ
drastically at higher (2,3 TeV) center of mass energies. Starting from these
conclusions, we argue that a complete one-loop calculation in the energy region
below 1 TeV does not seem to need extra two-loop corrections, in spite of the
relatively large size of the one-loop effects.Comment: 15 pages, 1 Encapsulated PostScript figur
Supersymmetry Tests from a Combined Analysis of Chargino and Charged Higgs Boson Pair Production at a 1 TeV Linear Collider
We consider the production of chargino and charged Higgs boson pairs at
future linear colliders for c.m. energies in the one TeV range. Working in the
MSSM under the assumption of a "moderately" light SUSY scenario, we compute the
leading (double) and next-to leading (linear) supersymmetric logarithmic terms
of the so-called "Sudakov expansion" at one loop. We show that a combined
analysis of the slopes of the chargino and of the charged Higgs production
cross sections would offer a simple possibility for determining for
large () values and an allowed strip in the () plane. This
could provide a strong consistency test of the considered supersymmetric model.Comment: 4 pages, 4 Encapsulated PostScript Figure
Weak Interaction Sum Rules for Polarized top-antitop Production at LHC
We consider two polarization asymmetries in the process of top-antitop
production at LHC. We show that the theoretical predictions for these two
quantities, at the strong and electroweak partonic one-loop level, are free of
QCD and QED effects. At this perturbative level we derive two sum rules, that
relate measurable quantities of top-antitop production to genuinely weak
inputs. This would allow to perform two independent tests of the candidate
theoretical model, with a precision that will be fixed by the future
experimental accuracies of the different polarization measurements. A tentative
quantitative illustration of this statement for a specific MSSM scenario is
enclosed, and a generalization to include two other future realistic
measurements is also proposed.Comment: 13 pages, 3 figures, local report number adde
Two-loop electroweak corrections at high energies
We discuss two-loop leading and angular-dependent next-to-leading logarithmic
electroweak virtual corrections to arbitrary processes at energies above the
electroweak scale. The relevant Feynman diagrams involving soft-collinear gauge
bosons gamma, Z, W, have been evaluated in eikonal approximation. We present
results obtained from the analytic evaluation of massive loop integrals. To
isolate mass singularities we used the Sudakov method and alternatively the
sector decomposition method in the Feynman-parameter representation.Comment: 5 pages. Talk presented by S.P. at the International Symposium on
Radiative Corrections RADCOR 2002, September 8-13, Kloster Banz, Germany. To
appear in the proceeding
Phase diagram of the lattice Wess-Zumino model from rigorous lower bounds on the energy
We study the lattice N=1 Wess-Zumino model in two dimensions and we construct
a sequence of exact lower bounds on its ground state energy
density , converging to in the limit . The bounds
can be computed numerically on a finite lattice with sites and
can be exploited to discuss dynamical symmetry breaking. The transition point
is determined and compared with recent results based on large-scale Green
Function Monte Carlo simulations with good agreement.Comment: 32 pages, 12 figure
Twist-three at five loops, Bethe Ansatz and wrapping
We present a formula for the five-loop anomalous dimension of N=4 SYM
twist-three operators in the sl(2) sector. We obtain its asymptotic part from
the Bethe Ansatz and finite volume corrections from the generalized Luescher
formalism, considering scattering processes of spin chain magnons with virtual
particles that travel along the cylinder. The complete result respects the
expected large spin scaling properties and passes non-trivial tests including
reciprocity constraints. We analyze the pole structure and find agreement with
a conjectured resummation formula. In analogy with the twist-two anomalous
dimension at four-loops, wrapping effects are of order log^2 M/M^2 for large
values of the spin.Comment: 19 page
Conformal a-anomaly of some non-unitary 6d superconformal theories
We compute the conformal anomaly a-coefficient for some non-unitary (higher
derivative or non-gauge-invariant) 6d conformal fields and their
supermultiplets. We use the method based on a connection between 6d
determinants on S^6 and 7d determinants on AdS_7. We find, in particular, that
(1,0) supermultiplet containing 4-derivative gauge-invariant conformal vector
has precisely the value of a-anomaly as attributed in arXiv:1506.03807 (on the
basis of R-symmetry and gravitational 't Hooft matching) to the standard (1,0)
vector multiplet. We also show that higher derivative (2,0) 6d conformal
supergravity coupled to exactly 26 (2,0) tensor multiplets has vanishing
a-anomaly. This is the 6d counterpart of the known fact of cancellation of the
conformal anomaly in the 4d system of N=4 conformal supergravity coupled to 4
vector N=4 multiplets. In the case when 5 of tensor multiplets are chosen to be
ghost-like and the conformal symmetry is spontaneously broken by a quadratic
scalar constraint the resulting IR theory may be identified with (2,0) Poincare
supergravity coupled to 21=26-5 tensor multiplets. The latter theory is known
to be special: it is gravitational anomaly free and results upon
compactification of 10d type IIB supergravity on K3.Comment: 22 pages. v3: minor comments and references added, appendix expanded;
v4: minor correction
Three loop anomalous dimensions of twist-3 gauge operators in N=4 SYM
We propose a closed expression for the three loop anomalous dimension of a
class of twist-3 operators built with gauge fields and covariant derivatives.
To this aim, we solve the long-range Bethe Ansatz equations at finite spin and
provide a consistent analytical formula obtained assuming maximal
transcendentality violation as suggested by the known one-loop anomalous
dimension. The final result reproduces the universal cusp anomalous dimension
and obeys recursion relations inspired by the principle of reciprocity
invariance.Comment: 20 pages, JHEP styl
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