Instantons in lepton pair production

Brandenburg, A.; Ringwald, Andreas; Utermann, Andre

doi:10.1016/j.nuclphysb.2006.07.020

Cited by 9 publications

(10 citation statements)

References 79 publications

(100 reference statements)

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“…For the sake of symmetry we choose to eliminate the tensor h µν ab, 48 . Equation (30) implies a relation of the type…”

Section: Double Polarized Casementioning

confidence: 99%

“…On the other hand data for π − N → µ − µ + X taken at CERN [41,42] and at Fermilab [43] are in disagreement with the Lam-Tung relation. In particular, an unexpectedly large cos 2φ modulation of the cross section was observed, and in the meantime different explanations for this phenomenon have been put forward in the literature [44,45,46,47,48,49,50]. In Ref.…”

Section: Angular Distribution Of the Cross Sectionmentioning

confidence: 99%

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Dilepton production from polarized hadron hadron collisions

2009

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In this paper we present a comprehensive formalism for dilepton production from the collision of two polarized spin-1 2 hadrons by identifying the general angular distribution of the cross section in combination with a complete set of structure functions. The various structure functions are computed in the parton model approximation where we mainly consider the case when the transverse momentum of the dilepton pair is much smaller than its invariant mass. In this kinematical region dilepton production can be described in terms of transverse momentum dependent parton distributions.

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“…For the sake of symmetry we choose to eliminate the tensor h µν ab, 48 . Equation (30) implies a relation of the type…”

Section: Double Polarized Casementioning

confidence: 99%

Section: Angular Distribution Of the Cross Sectionmentioning

confidence: 99%

Dilepton production from polarized hadron hadron collisions

2009

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“…The π-nucleus DY data [13][14][15] show a significant violation of this relation, which calls for a nonperturbative leading-twist mechanism beyond collinear factorization. The Boer-Mulders effect provides such a mechanism within the TMD factorization framework [34], though alternative mechanisms have also been proposed [45][46][47][48][49]. Indications for the violation of the Lam-Tung relation were also observed in pp-and pd-induced DY [50].…”

Section: Introductionmentioning

confidence: 99%

Pion transverse momentum dependent parton distributions in a light-front constituent approach, and the Boer-Mulders effect in the pion-induced Drell-Yan process

Pasquini

Schweitzer

2014

Phys. Rev. D

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At leading twist the transverse-momentum dependent parton distributions of the pion consist of two functions, the unpolarized f1,π(x, k 2 ⊥ ) and the Boer-Mulders function h ⊥ 1,π (x, k 2 ⊥ ). We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function f1,π(x) are in very good agreement with available parameterizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient ν in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with data, and carefully discuss the range of applicability of our approach.

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“…[36,37]. To get reasonable probabilities, one should consider models with tunneling rates raised by dynamical mechanisms [38][39][40][41], resort to strong coupling [42,43] or exotica [44].…”

Section: Introductionmentioning

confidence: 99%

High-energy limit of collision-induced false vacuum decay

Demidov

Levkov

2015

J. High Energ. Phys.

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We develop a consistent semiclassical description of field-theoretic collisioninduced tunneling at arbitrary high collision energies. As a playground we consider a (1 + 1)-dimensional false vacuum decay initiated by a collision of N particles at energy E, paying special attention to the realistic case of N = 2 particles. We demonstrate that the cross section of this process is exponentially suppressed at all energies. Moreover, the respective suppressesion exponent F N (E) exhibits a specific behavior which is significant for our semiclassical method and assumed to be general: it decreases with energy, reaches absolute minimum F = F min (N ) at a certain threshold energy E = E rt (N ), and stays constant at higher energies. We show that the minimal suppression F min (N ) and threshold energy can be evaluated using a special class of semiclassical solutions which describe exponentially suppressed transitions but nevertheless evolve in real time. Importantly, we argue that the cross section at energies above E rt (N ) is computed perturbatively in the background of the latter solutions, and the terms of this perturbative expansion stay bounded in the infinite-energy limit. Transitions in the high-energy regime proceed via emission of many soft quanta with total energy E rt ; the energy excess E − E rt remains in the colliding particles till the end of the process.

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Instantons in lepton pair production

Cited by 9 publications

References 79 publications

Dilepton production from polarized hadron hadron collisions

Dilepton production from polarized hadron hadron collisions

Pion transverse momentum dependent parton distributions in a light-front constituent approach, and the Boer-Mulders effect in the pion-induced Drell-Yan process

High-energy limit of collision-induced false vacuum decay

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