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Is dark matter made of mirror matter? Evidence from cosmological data ; Wallemacq, Quentin in Physics Letters B (2014), 729 We present new fast numerical simulations of cosmic microwave background and large scale structure in the case in which the cosmological dark matter is made entirely or partly of mirror matter. We ... [more ▼] We present new fast numerical simulations of cosmic microwave background and large scale structure in the case in which the cosmological dark matter is made entirely or partly of mirror matter. We consider scalar adiabatic primordial perturbations at linear scales in a flat Universe. The speed of the simulations allows us for the first time to use Markov Chain Monte Carlo analyses to constrain the mirror parameters. A Universe with pure mirror matter can fit very well the observations, equivalently to the case of an admixture with cold dark matter. In both cases, the analyses show a clear indication of the presence of a consistent amount of mirror dark matter, 0.05 < Ω_{mirror} h^2 < 0.12. [less ▲] Detailed reference viewed: 42 (11 ULg)On the observability of the quark orbital angular momentum distribution Courtoy, Aurore ; ; et al in Physics Letters B (2014), 731(0), 141-147 Detailed reference viewed: 15 (0 ULg)Spin-orbit correlations in the nucleon Lorce, Cédric in Physics Letters B (2014) Detailed reference viewed: 14 (1 ULg)QCD description of charmonium plus light meson production in p̄-N annihilation ; Semenov-Tyan-Shanskiy, Kirill ; in Physics Letters B (2013), 724 Detailed reference viewed: 16 (2 ULg)Extraction of $\alpha_s$ from deep inelastic scattering at large $x$ Courtoy, Aurore ; in Physics Letters B (2013), B726 Detailed reference viewed: 12 (0 ULg)Wilson lines and orbital angular momentum Lorce, Cédric in Physics Letters B (2013), B719 We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by ... [more ▼] We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated over. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same. [less ▲] Detailed reference viewed: 17 (2 ULg)Reassessing the importance of the colour-singlet contributions to direct $J/ + W$ production at the LHC and the Tevatron Lansberg, Jean-Philippe ; Lorce, Cédric in Physics Letters B (2013), B726 We show that the colour-singlet contributions to the hadroproduction of $J/\Psi$ in association with a W boson are sizable, if not dominant over the colour-octet contributions. They are of two kinds, $sg ... [more ▼] We show that the colour-singlet contributions to the hadroproduction of $J/\Psi$ in association with a W boson are sizable, if not dominant over the colour-octet contributions. They are of two kinds, $sg\toJ/\Psi+c+W$ at $\alpha^3s\alpja$ and $q\overline q' \to\gamma^\star /Z ^\star W\to J/\Psi W$ at order $\alpha^3$. These have not been considered in the literature until now. Our conclusion is that the hadroproduction of a $J/\Psi$ in association with a W boson cannot be claimed as a clean probe of the colour-octet mechanism. The rate are small even at the LHC and it will be very delicate to disentangle the colour-octet contributions from the sizable colour-singlet ones and from the possibly large double-parton-scattering contributions. During this analysis, we have also noted that, for reactions such as the production of a $J/\Psi$ by light quark–antiquark fusion, the colour-singlet contribution via an off-shell photon is of the order of the expectation from the colour-octet contribution via an off-shell gluon. This is relevant for inclusive production at low energies close to the threshold. Such an observation also likely extends to other processes naturally involving light-quark annihilation. [less ▲] Detailed reference viewed: 21 (4 ULg)Pretzelosity TMD and Quark Orbital Angular Momentum Lorce, Cédric ; in Physics Letters B (2012), B710 We study the connection between the quark orbital angular momentum and the pretzelosity transverse momentum dependent parton distribution function. We discuss the origin of this relation in quark models ... [more ▼] We study the connection between the quark orbital angular momentum and the pretzelosity transverse momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum. [less ▲] Detailed reference viewed: 12 (1 ULg)Higgs Central Exclusive Production Cudell, Jean-René ; ; in Physics Letters B (2012), 706 We tune the calculation of central exclusive Higgs production to the recent CDF central exclusive dijet data, and predict the cross section for the exclusive production of Higgs boson at the LHC. It is ... [more ▼] We tune the calculation of central exclusive Higgs production to the recent CDF central exclusive dijet data, and predict the cross section for the exclusive production of Higgs boson at the LHC. It is always below 1 fb, and below 0.3 fb after experimental cuts. [less ▲] Detailed reference viewed: 17 (3 ULg)Frustrated symmetries in multi-Higgs-doublet models Ivanov, Igor ; Keus, Venus in Physics Letters B (2011), 695(5), 459-462 Within multi-Higgs-doublet models, one can impose symmetries on the Higgs potential, either discrete or continuous, that mix several doublets. In two-Higgs-doublet model any such symmetry can be conserved ... [more ▼] Within multi-Higgs-doublet models, one can impose symmetries on the Higgs potential, either discrete or continuous, that mix several doublets. In two-Higgs-doublet model any such symmetry can be conserved or spontaneously violated after the electroweak symmetry breaking (EWSB), depending on the coefficients of the potential. With more than two doublets, there exist symmetries which are always spontaneously violated after EWSB. We discuss the origin of this phenomenon and show its similarity to frustration in condensed matter physics. [less ▲] Detailed reference viewed: 42 (16 ULg)Associated production of one particle and a Drell-Yan pair in hadronic collisions Ceccopieri, Federico in Physics Letters B (2011), 703(4), 491-497 We propose a collinear factorization formula for the associated production of one particle and a Drell-Yan pair in hadronic collisions. It is shown that additional collinear singularities appearing in the ... [more ▼] We propose a collinear factorization formula for the associated production of one particle and a Drell-Yan pair in hadronic collisions. It is shown that additional collinear singularities appearing in the next-to-leading order calculations that cannot be factorized into parton and fragmentation functions are systematically renormalized by introducing fracture functions. Next-to-leading order coefficient functions for cross-sections double differential in the fractional energy of the identified hadron and lepton pair invariant mass are presented. [less ▲] Detailed reference viewed: 18 (11 ULg)Enhancement effects in exclusive ππ and ρπ production in γ* γ scattering Courtoy, Aurore ; in Physics Letters B (2009), 675(1), 38-42 The exclusive ππ and ρπ production in hard γ* γ scattering in the forward kinematical region where the virtual photon is highly off-shell is studied using the γ → π- Transition Distribution Amplitudes ... [more ▼] The exclusive ππ and ρπ production in hard γ* γ scattering in the forward kinematical region where the virtual photon is highly off-shell is studied using the γ → π- Transition Distribution Amplitudes obtained in realistic models for the pion. For ρπ production we confirm the previous estimates before QCD evolution. Nevertheless, once evolution is taken into account this cross section grows one order of magnitude. In the case of ππ production we have evaluated the cross section including the pion pole contribution. We observe that this contribution is responsible for an enhancement of two orders of magnitude with respect to the cross section evaluated without the pion pole term. © 2009 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 8 (1 ULg)Variations on leptogenesis Aristizabal Sierra, Diego ; ; in Physics Letters B (2008), 659 We study variations of the standard leptogenesis scenario that can arise if an additional mass scale related to the breaking of some new symmetry (as for example a flavor or the B–L symmetry) is present ... [more ▼] We study variations of the standard leptogenesis scenario that can arise if an additional mass scale related to the breaking of some new symmetry (as for example a flavor or the B–L symmetry) is present below the mass MN1 of the lightest right-handed Majorana neutrino. Our scheme is inspired by U(1) models of flavor à la Froggatt–Nielsen, and involves new vectorlike heavy fields F. We show that depending on the specific hierarchy between MN1 and the mass scale of the fields F, qualitatively different realizations of leptogenesis can emerge. We compute the CP asymmetries in N1 decays in all the relevant cases, and we conclude that in most situations leptogenesis could be viable at scales much lower than in the standard scenario. [less ▲] Detailed reference viewed: 5 (0 ULg)Unitarisation and black-disk limit at the LHC in the presence of a hard pomeron Cudell, Jean-René ; in Physics Letters B (2008), 662(5), 417-423 Recent models of soft diffraction include a hard pomeron pole besides the usual soft term. Such models violate the black-disk limit around Tevatron energies, so that they need to be supplemented by a ... [more ▼] Recent models of soft diffraction include a hard pomeron pole besides the usual soft term. Such models violate the black-disk limit around Tevatron energies, so that they need to be supplemented by a unitarisation scheme. Two standard schemes are considered in this Letter, and we show that they lead to an uncertainty at the LHC much larger than previously estimated. We also examine the signature of unitarisation on various small-t observables, the slope in t of the elastic cross section, or the ratio of the real to imaginary parts of the scattering amplitude, and show that the existence of a unitarised hard pomeron in soft scattering may be confirmed by LHC data. (C) 2008 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 32 (7 ULg)New contributions to heavy-quarkonium production Lansberg, Jean-Philippe ; Cudell, Jean-René ; in Physics Letters B (2006), 633(2-3), 301-308 We reconsider quarkonium production in a field-theoretical setting and we show that the lowest-order mechanism for heavy-quarkonium production receives in general contributions from two different cuts ... [more ▼] We reconsider quarkonium production in a field-theoretical setting and we show that the lowest-order mechanism for heavy-quarkonium production receives in general contributions from two different cuts. The first one corresponds to the usual colour-singlet mechanism. The second one has not been considered so far. We treat it in a gauge-invariant manner, and introduce new 4-point vertices, suggestive of the colour-octet mechanism. These new objects enable us to go beyond the static approximation. We show that the contribution of the new cut can be as large as the usual colour-singlet mechanism at high P-T for J/psi. In the psi' case, theoretical uncertainties are shown to be large and agreement with data is possible. (c) 2005 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 18 (6 ULg)Two-Higgs-doublet model from the group-theoretic perspective Ivanov, Igor in Physics Letters B (2006), 632(2-3), 360-365 In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic “hyperspinor”. We decompose the Higgs potential of this model into irreducible representations of the SU(2 ... [more ▼] In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic “hyperspinor”. We decompose the Higgs potential of this model into irreducible representations of the SU(2) group of transformations of this hyperspinor. We discuss invariant combinations of Higgs potential parameters λi that arise in this decomposition and provide simple and concise sets of conditions for the hidden Z2-symmetry, Peccei–Quinn symmetry, and explicit CP-conservation in 2HDM. We show that some results obtained previously by brute-force calculations are reduced to simple linear algebraic statements in our approach. [less ▲] Detailed reference viewed: 15 (1 ULg)Excited [70,l(+)] baryons in large N-c QCD ; Stancu, Floarea in Physics Letters B (2005), 631(1-2), 7-15 The masses of the positive parity [70, 0(+)] and [70, 2(+)] non-strange baryons are calculated in large N-c QCD by considering the most dominant operators in an 1/N-c expansion. The approach is based on ... [more ▼] The masses of the positive parity [70, 0(+)] and [70, 2(+)] non-strange baryons are calculated in large N-c QCD by considering the most dominant operators in an 1/N-c expansion. The approach is based on the introduction of an excited core, obtained after the last particle (an excited quark) has been removed. Configuration mixing is neglected, for simplicity. Although being a sub-leading 1/Nc order, we find that the spin-spin interaction plays a dominant role in describing the data. The role of No operators is also pointed out. We show how the contribution of the linear term in Nc, of the spin-spin and of the spin-orbit terms vary with the excitation energy. (c) 2005 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 18 (1 ULg)Production of orbitally excited vector mesons in diffractive DIS ; Ivanov, Igor in Physics Letters B (2005), 622(1-2), 55-62 Within the kt-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the ρ(1450)/ρ(1700) case. At ... [more ▼] Within the kt-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the ρ(1450)/ρ(1700) case. At small Q2, orbital excitation of light quarkonia is found to dominate over radial excitations in diffractive production. We predict strong suppression of the production of orbital excitations by longitudinal photons, which leads to very small σL/σT ratio. At small Q2, the s-channel helicity violating transitions contribute not, vert, similar10–15% of the transverse cross section and not, vert, similar50% of the longitudinal cross section. We also study mixing between radial and orbital excitations and determine strategies towards clarification of S-wave/D-wave assignment to ρ(1450) and ρ(1700) mesons. The results are compared with the experimental data available, and predictions for future experiments are given. [less ▲] Detailed reference viewed: 34 (0 ULg)Dynamical study of the pentaquark antidecuplet Stancu, Floarea in Physics Letters B (2004), 595 Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Theta(+) belongs. The framework is a constituent quark model where the short ... [more ▼] Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Theta(+) belongs. The framework is a constituent quark model where the short-range interaction has a flavour-spin structure. In this model the lowest pentaquarks have positive parity. Each antidecuplet member is described by a variational solution with the Pauli principle properly taken into account. By fitting the mass of Theta(+) of minimal content uudd, the mass of Xi(--), of minimal content ddss (u) over bar, is predicted at approximately 1960 MeV. The influence of the octet-antidecuplet mixing on the masses of the Y = I and 0 pentaquarks is considered within the same model and the role of the hyperfine interaction in this mixing is pointed out. (C) 2004 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 13 (3 ULg)A model for the off-forward structure functions of the pion ; Cudell, Jean-René ; Cugnon, Joseph et al in Physics Letters B (2004), 587(3-4), 189-200 We extend our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward y*pi -->. gamma*pi scattering ... [more ▼] We extend our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward y*pi -->. gamma*pi scattering amplitude is evaluated in the chiral limit (m(pi) = 0) and related to the twist-two and twist-three generalised parton distributions H, H-3, (H) over tilde (3). Non-perturbative effects, linked to the size of the pion and still preserving gauge invariance, are included. Remarkable new relations between H, H3 and (H) over tilde (3) are obtained and discussed. (C) 2004 Published by Elsevier B.V. [less ▲] Detailed reference viewed: 17 (3 ULg) |
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