| 1. |
- Armesto, Nestor, et al.
(författare)
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Coherence effects and broadening in medium-induced QCD radiation off a massive q(q)over-bar antenna
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :1
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Tidskriftsartikel (refereegranskat)abstract
- Studies of medium-induced QCD radiation usually rely on the calculation of single-gluon radiation spectrum off an energetic part on traversing an extended colored medium. Recently, the importance of interference effects between emitters in the medium has been explored. In this work we extend previous studies by calculating the single-gluon coherent spectrum off an antenna consisting of a massive quark-antiquark pair. Interferences dominate the spectrum of soft gluons, which are mainly emitted outside of the cone made by the antenna opening angle, while the antenna results in a superposition of independent emitters above a critical gluon energy scale. We study the interplay between the dead-cone effect and medium-induced jet broadening in both cases of soft and hard gluons and present results on energy loss distributions.
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| 2. |
- Mehtar-Tani, Yacine, et al.
(författare)
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Jets in QCD media: From color coherence to decoherence
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 707:1, s. 156-159
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Tidskriftsartikel (refereegranskat)abstract
- We investigate soft gluon radiation off a quark-antiquark antenna in both color singlet and octet configurations traversing a dense medium. We demonstrate that, in both cases, multiple scatterings lead to a gradual decoherence of the antenna radiation as a function of the medium density. In particular, in the limit of a completely opaque medium, total decoherence is obtained, i.e., the quark and the antiquark radiate as independent emitters in vacuum, thus losing memory of their origin. (C) 2011 Elsevier B.V. All rights reserved.
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| 3. |
- Mehtar-Tani, Yacine, et al.
(författare)
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The radiation pattern of a QCD antenna in a dense medium
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :10
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the radiation spectrum off a q (q) over bar pair of a fixed opening angle theta(q (q) over bar) traversing a medium of length L. Multiple interactions with the medium are handled in the harmonic oscillator approximation, valid for soft gluon emissions. We discuss the time-scales relevant to the decoherence of correlated partons traversing the medium and demonstrate how this relates to the hard scale that govern medium-induced radiation. For large angle radiation, the hard scale is given by Q(hard) = max(r(perpendicular to)(-1), Q(s)), where r(perpendicular to) = theta L-qq is the probed transverse size and Q(s) is the maximal transverse momentum accumulated by the emitted gluon in the medium. These situations define in turn two distinct regimes, which we call "dipole" and "decoherence" regimes, respectively, which are discussed in detail. A feature common to both cases is that coherence of the radiation is restored at large transverse momenta, k(perpendicular to) > Q(hard).
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| 4. |
- Mehtar-Tani, Yacine, et al.
(författare)
-
The radiation pattern of a QCD antenna in a dilute medium
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :4
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative interferences in the multi-parton shower is the building block of QCD jet physics in vacuum. The presence of a hot medium made of quarks and gluons is expected to alter this interference pattern. To study these effects, we derive the gluon emission spectrum off a color-correlated quark-antiquark pair (antenna) traversing a colored medium to first order in the medium density. The resulting induced gluon distribution is found to be governed by the hardest scale of the problem. In our setup, this can either be the inverse antenna transverse size, r(perpendicular to)(-1), or the scale related to the transverse color correlation length in the medium, which is given by the Debye mass m(D). This emerging scale opens the angular phase space of emissions off the antenna compared to the vacuum case and gives rise to a typical transverse momentum of the medium-induced emitted gluons, < k(perpendicular to)(2)>(med) similar to max(r(perpendicular to)(-1)m(D)). Above the hard scale interference effects suppress the spectrum resulting in the restoration of vacuum coherence.
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