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Tibor Torma

Publications and source records attributed to Tibor Torma.

7 recordsLinked to original sources
arXiv2001

Nonconservation of global quantum numbers in RSbar-type models

In Randall-Sundrum type scenarios the effective size of the extra dimension remains unconstrained. A TeV-scale brane tension without orbifold boundary conditions would allow phenomenologically observable processes at high energy colliders. Among others, the brane could fragment into bubbles that fly away for good or return within a time TeV is reached, bubbles with 1/TeV size are copiously produced. At lower sqrt{s}, smaller bubbles can be produced (if they exist) with strongly suppressed probability.

hep-ph↗
arXiv2000

Intersecting branes with an arbitrary excess angle

We find all possible static embeddings of a 4-brane in any dimension-6 spacetime with 4-dimensional Poincare symmetry and a negative cosmological constant, subject to orbifolding across the brane. Our new solutions allow intersecting branes at an angle determined by a new dynamical parameter. A collection of branes intersecting in one 3-brane allows an arbitrary excess angle that can be related to a vacuum density along the intersection. The 3-brane must be stabilized by additional fine-tuned interactions. We also note that localization of gravity is tied to the approximate fine tuning of the brane tensions.

hep-th↗
arXiv1999

Charmonium production at neutrino factories

At existing and planned neutrino factories (high energy and high intensity neutrino beam facilities) precision studies of QCD in neutrino-nucleon interactions are a realistic opportunity. We investigate charmonium production in fixed target neutrino experiments. We find that $J/ψ$ production in neutrino-nucleon collision is dominated by the color octet $^3S_1$ NRQCD matrix element in a neutral current process, which is not accessible in photo or leptoproduction. Neutrino experiments at a future Muon Collider will acquire sufficient event rate to accurately measure color octet matrix element contributions. The currently running high energy neutrino experiments, NOMAD and NuTeV could also observe several such events.

hep-ph↗
arXiv1997

QCD corrections to B -> J/psi + anything

We calculate the branching ratio for B -> J/psi + anything, within the color-singlet approximation for J/psi production, but including perturbative QCD corrections beyond the leading logarithm approximation. Such higher order corrections are necessary, in order to obtain a result that is not strongly dependent on the renormalization scale. As in the earlier work of Bergstrom and Ernstrom, we use a double expansion in alpha_s and in the small ratio of Wilson coefficients L_0/L_2, to identify the dominant terms in the decay amplitude. We complete their work by calculating all the leading order terms in this double expansion. The predicted branching ratio is then BR(B -> J/psi + anything) = 0.09 (+1.1)(-0.3) %, which is well below the experimental value BR(experimental) = 0.80 (+-0.08) %. This confirms the suspicion that non-perturbative corrections to the color-singlet approximation for J/psi production in B decays are important.

hep-ph↗
arXiv1996

The Equivalence Theorem and infrared divergences

We look at the Equivalence Theorem as a statement about the absence of polynomial infrared divergences when $m_W \rightarrow 0$. We prove their absence in a truncated toy model and conjecture that, if they exist at all, they are due to couplings between light particles.

hep-ph↗
arXiv1994

Supersymmetry and Stationary Solutions in Dilaton-Axion Gravity

New stationary solutions of $4$-dimensional dilaton-axion gravity are presented, which correspond to the charged Taub-NUT and Israel-Wilson-Perjes (IWP) solutions of Einstein-Maxwell theory. The charged axion-dilaton Taub-NUT solutions are shown to have a number of interesting properties: i) manifest $SL(2,R)$ symmetry, ii) an infinite throat in an extremal limit, iii) the throat limit coincides with an exact CFT construction. The IWP solutions are shown to admit supersymmetric Killing spinors, when embedded in $d=4,N=4$ supergravity. This poses a problem for the interpretation of supersymmetric rotating solutions as physical ground states. In the context of $10$-dimensional geometry, we show that dimensionally lifted versions of the IWP solutions are dual to certain gravitational waves in string theory.

hep-th↗