122212810
Carruthers’ theorem for any spin and parastatistics
SummaryIt is shown that Carruthers’ theorem (that particle multiplets of half-integral isospin cannot be self-conjugate) holds even for particles which obey the general parastatistics instead of the usual Bose or Fermi statistics.RiassuntoSi dimostra che il teorema di Carruther (sull’impossibilità di autoconiugazione per multipletti di particelle con isospin semintero) value anche per particelle che obbediscono solo alla parastatistica generale invece che alla statistica consueta di Bose o Fermi.
120662802
Commutation relations among members of internal-symmetry multiplets
120740147
Relativistic wave equations: proper Lorentz invariance and invariance under discrete transformations
Considering the standard form i∂ψ/∂t=Hψ [with ψ transforming according to D(0,s)⊕D(s,0)] of wave equations for free particles of arbitrary spin, we determined in a recent paper the admissible forms of H consistent with invariance of the equation under the Poincare group and under T, C, and P. Here we show that even if T and C invariance is not imposed, the admissible Hamiltonians are the same (apart from one extra possibility H = E). Expressed differently, except for the trivial case H = E, invariance of free‐particle equations under the connected Poincare group and P implies T and C also.
124611352
Quantization of wave equations for zero-mass particles with invariant helicities
SummaryIn a recent paper we constructed relativistic wave equations in the standard formi∂ψ/∂t=Hψ (ψ∼D(0,s) ⊕D(s, 0)) for zeromass particles with invariant helicities. Outlining the essential steps only, we present in this short paper the details of second quantization of these equations.RiassuntoIn un recente articolo abbiamo costruito le equazioni d’onda relativistiche nella forma normalei∂ψ/∂t=Hψ (ψ∼D(0,s) ⊕D(s, 0)) per particelle di massa nulla con elicità invarianti. Delineando solo i passaggi principali presentiamo in questo breve articolo i dettagli della seconda quantizzazione di queste equazioni.РеэюмеВ недавней работе мы сконструировали релятивистские уравнения в стандартной форме i∂ψ/∂t = Нψ (ψ∼D(0, в) ⊕ D(s, 0)) для частиц нулевой массы с инвариантными спиральностями. Намечая лищь основные зтапы, мы в зтой короткой статье приводим детали только вторичного квантования зтих уравнений.
118727721
Semi-coherent states of the quantum harmonic oscillator
SummaryIt is shown that there exists for the quantum harmonic oscillator a large class of « semi-coherent » states, which represent harmonically oscillating wave packets whose « spread » or « size » remains constant. These states are different from the coherent states in not having the minimum value 1/2ħ for the uncertainty product Δx·Δp.RiassuntoSi dimostra che esiste per l’oscillatore armonico quantistico una grande varietà di stati « semicoerenti », che rappresentano pacchetti d’onde oscillanti armonicamente, la cui « diffusione » o « dimensione » rimane costante. Questi stati differiscono dagli stati coerenti per non avere il valore minimo 1/2ħ per il prodotto d’indeterminazione Δx·Δp.РезюмеПоказывается, что для квантового гармонического осци ллятора существует б ольшой класс « полукоreр ентньIх» состояний, кот орые предст « полукоreрентньIх» состо яний, которые предста вляют гармони чески осциллирующие волновые пакеты, «разброс » или «разме ры » которых остаются постояннымгармонич ески осциллирующие волновые пакеты, «раз брос » или «размеры » которых остаются постоянными. Эти сост ояния отличаются от к огерентных состояни й тем, что не имеют мини мальной величины Р дл я произве или «размеры » которых остаются постоянными. Эти состояния отлича ются от когерентных с остояний тем, что не им еют минимальной вели чины Р для произведен ия неопределенносте й состояния отличаютс я от когерентных сост ояний тем, что не имеют минимальной величин ы Р для произведения н еопределенностей что не имеют минималь ной величины Р для про изведения неопредел енностей неопределенностей Ах Ар.
122825959
Rarita-Schwinger particles in homogeneous magnetic fields, and inconsistencies of spin-3/2 theories
The Rarita-Schwinger equation for a spin-$\frac{3}{2}$ particle with minimal electromagnetic coupling is solved completely in the case when a constant homogeneous external magnetic field $\mathcal{H}$ is present. It is shown that the spectrum of energy eigenvalues includes complex values if $\mathcal{H}$ is such that $\ensuremath{\eta}\ensuremath{\equiv}(\frac{2e\mathcal{H}}{3{m}^{3}})g1$, and further that the norm of the Rarita-Schwinger wave function (i.e., the total "charge" integral defined from the Lagrangian) which is positive definite for $\ensuremath{\eta}l1$ becomes indefinite (even after taking account of the constraints) when $\ensuremath{\eta}$ exceeds unity. These results confirm that the difficulties in quantization first discovered by Johnson and Sudarshan are a reflection of the indefiniteness of the norm which appears already at the $c$-number level, and suggest that the nature of the energy spectrum (whether or not complex values are present) in the presence of very large magnetic fields would provide a quick means of predicting whether such difficulties would arise in quantization.
54538817
Quark and gluon spin-2 form factors to two-loops in QCD
A bstractWe present complete two-loop radiative corrections to the graviton-quark-antiquark form factor G∗ → q$ \overline{q} $ and graviton-gluon-gluon form factor G∗ → g g in SU(N) gauge theory with nf light flavours using d-dimensional regularisation to all orders in ε = d − 4. Thisisanimportantingredienttonext-to-next-to-leadingorderQCDcorrections to hadronic scattering processes in models with large extra-dimensions where Kaluza-Klein graviton modes couple to Standard Model fields. We show that these form factors obey Sudakov integro-differential equation and the resulting cusp, collinear and soft anomalous dimensions coincide with those of electroweak vector boson and gluon form factors. We also find the universal behaviour of the infrared singularities in accordance with the proposal by Catani.
8021098
Next-to-leading order QCD corrections to the Drell-Yan cross section in models of TeV-scale gravity
Abstract The first results on next-to-leading order QCD corrections to graviton-induced processes in hadron collisions in models of TeV-scale gravity are presented focusing on the case of dilepton pair production in p ¯ p and pp collisions. Distributions in the invariant mass Q , the longitudinal fraction x F , the rapidity Y and the forward–backward asymmetry of the lepton pair are studied. The quantitative impact of the QCD corrections for searches of extra dimensions at hadron colliders is investigated. It turns out that at the LHC ( S = 14  TeV ) the K -factor is rather large ( K = 1.6 ) for large invariant mass Q of the lepton pair, indicating the importance of accounting for these QCD corrections in the experimental search for TeV-scale gravity. At the Tevatron, the K -factor does not substantially deviate from the Standard Model value. However, its inclusion is necessitated to make the cross section stable with respect to scale variations.
18381800
Can polarized Drell-Yan shed more light on the proton spin
We analyze polarized Drell-Yan process using the factorization method and derive operator definitions for polarized parton distribution functions. We demonstrate that a factorization analogous to that in the unpolarized Drell-Yan case holds in this process. We study the leading order gluonic contribution to the first moment of polarized Drell-Yan function and show that it is consistent with the results obtained from polarized deep inelastic scattering.
120091867
Extra dimension searches at hadron colliders to next-to-leading order-QCD
The quantitative impact of NLO-QCD corrections for searches of large and warped extra dimensions at hadron colliders are investigated for the Drell-Yan process. The K-factor for various observables at hadron colliders are presented. Factorisation, renormalisation scale dependence and uncertainties due to various parton distribution functions are studied. Uncertainties arising from the error on experimental data are estimated using the MRST parton distribution functions.
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.