119301953
Graviton plus vector boson production to NLO in QCD at the LHC
Abstract We present the next-to-leading order QCD corrections to the associated production of the vector gauge boson ( Z / W ± ) and the graviton in the large extra dimension model at the LHC. We estimate the impact of the QCD corrections on the total cross sections as well as the differential distributions of the gauge bosons and find that they are significant. We also study the dependence of the cross sections on the arbitrary factorization scale and show the reduction in the scale uncertainties at NLO level. Further, we discuss the ultraviolet sensitivity of the theoretical predictions.
121522381
GLUONIC CONTRIBUTIONS TO SPIN-DEPENDENT WEAK STRUCTURE FUNCTIONS: METHOD OF FACTORIZATION
We compute the gluonic contributions to the spin-dependent weak structure functions (i=1, 3, 4), using the factorization theorem in the minimal subtraction scheme, . We have considered the most general case where the quark flavor masses are distinguished and the gluons are off mass shell. The gluonic contribution to the first moment of is found to vanish and do not receive leading order gluonic contribution. These results are shown to be free of mass singularities.
15386012
Searching for signals of minimal length in extra dimensional models using dilepton production at hadron colliders
Theories of quantum gravity suggest the existence of a minimal length scale. It is interesting to speculate what the consequences of the existence of such a length scale would be for models of large extra dimensions, in particular, the ADD model. When ADD model is conflated with the minimal length scale scenario, processes involving virtual exchange of gravitons cease to be ulraviolet divergent. We study the production of dileptons at hadron colliders as an example of a process mediated by virtual gravitons. We find that the bounds we derive on the effective string scale are significantly different (in fact, less stringent) from those derived in the conventional ADD model, both at the upgraded Tevatron and the large hadron collider.
9952561
Testing TeV scale quantum gravity using Dijet production at the Tevatron
Dijet production at the Tevatron including effects of virtual exchanges of spin-2 Kaluza-Klein modes in theories with large extra dimensions is considered. The experimental dijet mass and angular distribution are exploited to obtain stringent limits ( > 1.2 TeV) on the effective string scale MS.
121827797
Finite tension strings in SU(2) gauge theory
Abstract The second-order field equations of the SU(2) Higgs model are studied and a new class of string solutions is obtained. The tension is finite and scale-dependent and the strings are of minus one unit flux.
119270253
NNLO QCD corrections to the resonant sneutrino/slepton production at hadron colliders
We present a complete next to next to leading order QCD corrections to the resonant sneutrino and charged slepton production cross sections at hadronic colliders such as the Tevatron and the Large Hadron Collider within the context of R-parity violating supersymmetric model. We have demonstrated the role of these corrections in reducing uncertainties resulting from renormalisation and factorisation scales and thereby making our predictions reliable. We have incorporated soft gluon effects at N 3 LO level in order to study the stability of our results under perturbation. The NNLO corrections are found to be large and significant. The results obtained in this article are also applicable to resonance production of any color-neutral scalar.
119922926
Massive Vector Field: Covariant Definition of Independent Components and Quantization
A new approach to the theory of the vector field is presented in which inelegant features like negative terms in the energy do not make an appearance at any stage. All components of the field are handled in a completely symmetric fashion and the explicitly covariant appearance of the theory is preserved in the process of quantization as well as in earlier stages. Though the special features which arise when the mass vanishes are pointed out, a detailed treatment of that case is not included here and will be given separately.
121389983
A reduction of the Kemmer equation and the singular behaviour of integer-spin relativistic Hamiltonians
Abstract A reduced form of the Kemmer equation for spin one particles is derived, wherein the wave function, which has no redundant components, transforms locally (unlike in earlier reductions). The reduced Hamiltonian is identical to the spin one specialisation of the general integer-spin Hamiltonian obtained from recent investigations on second quantizable relativistic wave equations having the Hamiltonian form. It is an observation from the present analysis that while the reduced equation is well defined for the non-zero helicity projections of the wave function, the first time derivative of the zero helicity part of the reduced wave function is essentially undefined (much as if this part described a scalar particle). This helps to explain the “improper” nature of the general Hamiltonian for integer spin.
120046449
Evaluation of the density matrix for an ensemble of anharmonic oscillators by a path integral approach
Considering the Feynman path integral representation for the configuration-space density matrix for an ensemble of anharmonic oscillators, we determine the ‘stationary paths’ near which the integrand remains stationary. By taking the path integral to be saturated by contributions from the neighborhood of the path which maximizes the integrand we evaluate the density matrix explicitly in analytic form. This seems to be the first such evaluation of a path integral for a system not describable by a quadratic Hamiltonian. We also comment briefly on the question of analyticity with respect to the perturbation parameter.
118914003
Wave equations for zero-mass particle with invariant helicities
SummaryWe present a brief discussion of the difficulties associated with taking the limitm→0 in massive-particle equations of the formi(∂ψ/∂t)=Hψ, in which ψ transforms according to theD(0,s)⊕D(s,0) representation of the homogeneous Lorentz group. It is pointed out that, though the HamiltonianH tends to a well-defined form asm→0, the resulting wave equation is still unsatisfactory as the invariant scalar product (in the space of solutions of the wave equation) has an unacceptable form. We observe that this difficulty is due to the indecomposability of the representation of the Poincaré group over wave functions transforming asD(0,s)⊕D(s,0) in the massless case. Making due allowance for this fact we obtain, in close parallel to the treatment for massive particles, wave equations for zero-mass particles with invariant helicities ±s. The relevant invariant scalar products are also determined.RiassuntoSi presenta una breve discussione associata con il limitem→0 in equazioni per particelle con massa della formai(∂ψ/∂t)=Hψ, in cuiψ si trasforma secondo la rappresentazioneD(0,s)⊕C(s,0) del gruppo di Lorentz omogeneo. Si mette in rilievo che, sebbene l’hamiltonianoH tenda ad una forma ben definita quandom→0, l’equazione d’onda risultante non è ancora soddisfacente in quanto il prodotto scalare invariante (nello spazio delle soluzioni dell’equazione d’onda) ha una forma inaccettabile. Si osserva che questa difficoltà è dovuta alla indecomponibilità della rappresentazione del gruppo di Poincaré rispetto alle funzioni d’onda che si trasformano comeD(0,s)⊕D(s, 0) nel caso senza massa. Tenendo dovuto conto di questo fatto si ottengono, in stretta analogia con il trattamento per particelle con massa, equazioni per particelle con massa nulla con elicità invarianti ±s. Si determinano anche i relativi prodotti scalari invarianti.РеэюмеВкратце обсуждаются трудности, воэникаюшие при переходе к пределуm→;0 в уравнениях видаi(∂ψ/∂t)=H у с отличной от нуля массой частиц, в которых ψ преобраэуется согласно представлениюD(0,s)⊕D(s, 0) однородной группы Лорентца. Отмечается, что хотя Гамильтониан Я стремится к хорощо иэвестному выражению приm→0, но окончательное волновое уравнение является неудовлетворит ельным, так как инвариантное скалярное проиэведение (в пространстве рещений волнового уравнения) имеет неприемлемый вид. Мы обнаруживаем, что зта трудность обусловлена неприводимостью представления группы Пуанкаре череэ волновые функции, преобраэуюшиеся, какD(0,s)⊕D(s,0) в случае нулевой массы. Учитывая зтот факт, мы, по аналогии с рассмотрением для частиц с отличной от нуля массой, получаем волновое уравнение для частиц нулевой массы с инвариантными спиральностями ±s. Также определяются соответствуюшие инвариантные скалярные проиэведения.
120717967
Method of characteristics and causality of field propagation
It is pointed out that the method of characteristics gives only a necessary condition (not a sufficient one) for causality of field propagation. It is shown that the usual theory of vector fields with anomalous magnetic moment coupling to an external magnetic field is noncausal, contrary to what has been believed, as one of its modes of propagation turns out to be tachyonic, with the velocity of light as minimum velocity.