A counter example to the Bloch-Nordsieck theorem in non-abelian gauge theories

Di'Lieto, C.; Gendron, S.; Halliday, I.G.; Sachrajda, C.T.

doi:10.1016/0550-3213(81)90554-x

Cited by 93 publications

(66 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In theories with massless charged particles, such as QCD, the cancellation of infrared singularities (soft and collinear) is significantly more subtle. The Bloch-Nordsieck theorem fails in QCD: summing inclusively over final state gluon radiation is insufficient to cancel all infrared singularities, even if the initial state consists only of massive quarks [23][24][25][26]. Nevertheless, even in QCD infrared divergences can be shown to cancel in certain contexts.…”

Section: Introductionmentioning

confidence: 99%

Infrared finiteness and forward scattering

et al. 2019

View full text Add to dashboard Cite

Infrared divergences have long been heralded to cancel in sufficiently inclusive crosssections, according to the famous Kinoshita-Lee-Nauenberg theorem which mandates an initial and final state sum. While well-motivated, this theorem is much weaker than necessary: for finiteness, one need only sum over initial or final states. Moreover, the cancellation generically requires the inclusion of the forward scattering process. We provide a number of examples showing the importance of this revised understanding: in e + e − → Z at next-to-leading order, one can sum over certain initial and final states with an arbitrary number of extra photons, or only over final states with a finite number of photons, if forward scattering is included. For Compton scattering, infrared finiteness requires the indistinguishability of hard forward-scattered electrons and photons. This implies that in addition to experimental limits on the energy and angular resolution, there must also be an experimental limit on the momentum at which electric charge can be observed. Similar considerations are required to explain why the rate for γγ to scatter into photons alone is infrared divergent but the rate for γγ to scatter into photons or charged particles is finite. This new understanding sheds light on the importance of including degenerate initial states in physical predictions, the relevance of disconnected Feynman diagrams, the importance of dressing initial or final-state charged particles, and the quest to properly define the S matrix.

show abstract

Section: Introductionmentioning

confidence: 99%

Infrared finiteness and forward scattering

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The reason for this is twofold: on the technical side such calculations are uncommon and technically challenging [52]. On the conceptual side, even if one makes the effort to compute a cross-section with full mass dependence for initial-state massive quarks and then subtracts all quasi-collinear singularities as appropriate for a massless MS subtraction, it is known that collinear factorization is violated starting at NNLO with two initial state massive fermions [53][54][55]. More about this topic can be found in the textbook by Collins [56, section 14.6].…”

Section: Is the Value Of µ B A Matter Of Choice Or Part Of The Theorementioning

confidence: 99%

Heavy-flavor parton distributions without heavy-flavor matching prescriptions

Bertone

Glazov

Mitov

et al. 2018

J. High Energ. Phys.

View full text Add to dashboard Cite

Abstract:We show that the well-known obstacle for working with the zero-mass variable flavor number scheme, namely, the omission of O(1) mass power corrections close to the conventional heavy flavor matching point (HFMP) µ b = m, can be easily overcome. For this it is sufficient to take advantage of the freedom in choosing the position of the HFMP. We demonstrate that by choosing a sufficiently large HFMP, which could be as large as 10 times the mass of the heavy quark, one can achieve the following improvements: 1) above the HFMP the size of missing power corrections O(m) is restricted by the value of µ b and, therefore, the error associated with their omission can be made negligible; 2) additional prescriptions for the definition of cross-sections are not required; 3) the resummation accuracy is maintained and 4) contrary to the common lore we find that the discontinuity of α s and pdfs across thresholds leads to improved continuity in predictions for observables. We have considered a large set of proton-proton and electron-proton collider processes, many through NNLO QCD, that demonstrate the broad applicability of our proposal.

show abstract

“…So far all calculations tend to calculate the next-to-leading twist correction to LO or NLO process. As such there is not conflict with the known violation of factorization at higher twist [108,109].…”

Section: Upcoming Developmentsmentioning

confidence: 89%

Jet modification in the next decade: A pedestrian outlook

Majumder

2015

Pramana - J Phys

View full text Add to dashboard Cite

Abstract. In this review, intended for non-specialists and beginners, we recount the current status of the theory of jet modification in dense matter. We commence with an outline of the "traditional" observables which may be calculated without recourse to event generators. These include single and double hadron suppression, nuclear modification factor versus reaction plane etc. All of these measurements are used to justify both the required underlying physical picture of jet modification as well as the final obtained values of jet transport coefficients. This is followed by a review of the more modern observables which have arisen with the ability to reconstruct full jets, and the challenges faced therein. This is followed by a preview of upcoming theoretical developments in the field and an outlook on how the interface between these developments, phenomenological improvements, and upcoming data will allow us to quantitatively determine properties of the medium which effect the modification of hard jets.

show abstract

A counter example to the Bloch-Nordsieck theorem in non-abelian gauge theories

Cited by 93 publications

References 9 publications

Infrared finiteness and forward scattering

Infrared finiteness and forward scattering

Heavy-flavor parton distributions without heavy-flavor matching prescriptions

Jet modification in the next decade: A pedestrian outlook

Contact Info

Product

Resources

About