scholarly journals Mixed EW-QCD two-loop amplitudes for $$ q\overline{q}\to {\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-} $$ and γ5 scheme independence of multi-loop corrections

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Matthias Heller ◽  
Andreas von Manteuffel ◽  
Robert M. Schabinger ◽  
Hubert Spiesberger
Keyword(s):  
Standard Model ◽  
Scattering Amplitude ◽  
Light Quark ◽  
Dimensional Regularization ◽  
Relative Order ◽  
Hard Scattering ◽  
Loop Amplitude ◽  
Loop Amplitudes

Abstract We perform a dedicated study of the $$ q\overline{q} $$ q q ¯ -initiated two-loop electroweak-QCD Drell-Yan scattering amplitude in dimensional regularization schemes for vanishing light quark and lepton masses. For the relative order α and αs one-loop Standard Model corrections, details of our comparison to the original literature are given. The infrared pole terms of the mixed two-loop amplitude are governed by a known generalization of the dipole formula and we show explicitly that exactly the same two-loop polarized hard scattering functions are obtained in both the standard ’t Hooft-Veltman-Breitenlohner-Maison γ5 scheme and Kreimer’s anticommuting γ5 scheme.

scholarly journals Two-parton scattering amplitudes in the Regge limit to high loop orders

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Simon Caron-Huot ◽  
Einan Gardi ◽  
Joscha Reichel ◽  
Leonardo Vernazza
Keyword(s):  
Scattering Amplitudes ◽  
Scattering Amplitude ◽  
Dimensional Regularization ◽  
High Energy ◽  
Logarithmic Order ◽  
Finite Radius ◽  
High Loop ◽  
Parton Scattering ◽  
Infrared Divergences ◽  
Regge Limit

Abstract We study two-to-two parton scattering amplitudes in the high-energy limit of perturbative QCD by iteratively solving the BFKL equation. This allows us to predict the imaginary part of the amplitude to leading-logarithmic order for arbitrary t-channel colour exchange. The corrections we compute correspond to ladder diagrams with any number of rungs formed between two Reggeized gluons. Our approach exploits a separation of the two-Reggeon wavefunction, performed directly in momentum space, between a soft region and a generic (hard) region. The former component of the wavefunction leads to infrared divergences in the amplitude and is therefore computed in dimensional regularization; the latter is computed directly in two transverse dimensions and is expressed in terms of single-valued harmonic polylogarithms of uniform weight. By combining the two we determine exactly both infrared-divergent and finite contributions to the two-to-two scattering amplitude order-by-order in perturbation theory. We study the result numerically to 13 loops and find that finite corrections to the amplitude have a finite radius of convergence which depends on the colour representation of the t-channel exchange.

scholarly journals D → Klv semileptonic decay using lattice QCD with HISQ at physical pion masses

2018 ◽  
Vol 175 ◽  
pp. 13027 ◽  
Author(s):  
Bipasha Chakraborty ◽  
Christine Davies ◽  
Jonna Koponen ◽  
G Peter Lepage
Keyword(s):  
Standard Model ◽  
Lattice Qcd ◽  
Semileptonic Decay ◽  
Light Quark ◽  
Form Factors ◽  
New Physics ◽  
Ckm Matrix ◽  
Quark Masses ◽  
The Standard Model ◽  
Fertile Ground

he quark flavor sector of the Standard Model is a fertile ground to look for new physics effects through a unitarity test of the Cabbibo-Kobayashi-Maskawa (CKM) matrix. We present a lattice QCD calculation of the scalar and the vector form factors (over a large q2 region including q2 = 0) associated with the D→ Klv semi-leptonic decay. This calculation will then allow us to determine the central CKM matrix element, Vcs in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rate. This form factor calculation has been performed on the Nf = 2 + 1 + 1 MILC HISQ ensembles with the physical light quark masses.

scholarly journals A quantum field-theoretical perspective on scale anomalies in 1D systems with three-body interactions

2019 ◽  
Vol 34 (35) ◽  
pp. 1950291 ◽  
Author(s):  
W. S. Daza ◽  
J. E. Drut ◽  
C. L. Lin ◽  
C. R. Ordóñez
Keyword(s):  
Energy Momentum Tensor ◽  
Scattering Amplitude ◽  
Theoretical Perspective ◽  
Dimensional Regularization ◽  
Momentum Tensor ◽  
Quantum Field ◽  
One Dimensional ◽  
Scattering States ◽  
Three Body ◽  
Canonical Quantum

We analyze, from a canonical quantum field theory (QFT) perspective, the problem of one-dimensional particles with three-body attractive interactions, which was recently shown to exhibit a scale anomaly identical to that observed in two-dimensional (2D) systems with two-body interactions. We study in detail the properties of the scattering amplitude including both bound and scattering states, using cutoff and dimensional regularization, and clarify the connection between the scale anomaly derived from thermodynamics to the nonvanishing non-relativistic trace of the energy–momentum tensor.

scholarly journals Hard scattering amplitude for the higher helicity components of the pion form factor

1997 ◽  
Vol 55 (11) ◽  
pp. 7107-7113 ◽  
Author(s):  
Fu-Guang Cao ◽  
Jun Cao ◽  
Tao Huang ◽  
Bo-Qiang Ma
Keyword(s):  
Form Factor ◽  
Scattering Amplitude ◽  
Pion Form Factor ◽  
Hard Scattering

η DECAYS WITH WASA DETECTOR

2005 ◽  
Vol 20 (02n03) ◽  
pp. 536-538
Author(s):  
◽  
ANDRZEJ KUPŚĆ
Keyword(s):  
Standard Model ◽  
Light Quark ◽  
Storage Rings ◽  
Low Energy ◽  
Eta Mesons ◽  
Valuable Source ◽  
Quark Masses ◽  
Experimental Programme ◽  
The Standard Model ◽  
Source Of Information

Experimental programme of eta decays carried out at WASA detector is presented. Not-so-rare eta decays are well suited as a low energy QCD laboratory. For example decay η→3π is a valuable source of information on light quark masses. In very rare eta decays such as η→e+e- and η→π°e+e- fundamental aspects of the Standard Model can be tested. Production reactions – sources of eta mesons for the decay studies at storage rings such as CELSIUS and COSY are discussed. Prospects of eta decay physics for WASA@COSY are presented.

scholarly journals Single-top-quark production in the t-channel at NNLO

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
John Campbell ◽  
Tobias Neumann ◽  
Zack Sullivan
Keyword(s):  
Standard Model ◽  
Cross Sections ◽  
Top Quark ◽  
Light Quark ◽  
Inclusive Cross Section ◽  
Single Top ◽  
Top Quark Production ◽  
Quark Production ◽  
Jet Cross Sections ◽  
Quark Line

Abstract We present a calculation of t-channel single-top-quark production and decay in the five-flavor scheme at NNLO. Our results resolve a disagreement between two previous calculations of this process that found a difference in the inclusive cross section at the level of the NNLO coefficient itself. We compare in detail with the previous calculations at the inclusive, differential and fiducial level including b-quark tagging at a fixed scale μ = mt. In addition, we advocate the use of double deep inelastic scattering (DDIS) scales (μ2 = Q2 for the light-quark line and μ2 = Q2 + $$ {m}_t^2 $$ m t 2 for the heavy-quark line) that maximize perturbative stability and allow for robust scale uncertainties. All NNLO and NLO⊗NLO contributions for production and decay are included in the on-shell and vertex-function approximation. We present fiducial and differential results for a variety of observables used in Standard Model and Beyond Standard Model analyses, and find an important difference between the NLO and NNLO predictions of exclusive t + n-jet cross sections. Overall we find that NNLO corrections are crucial for a precise identification of the t-channel process.

Bremsstrahlung Calculations of Single Gauge-Boson Production on Linear Colliders in Context of "New Physics" Searching

2021 ◽  
Vol 24 (4) ◽  
pp. 317-325
Author(s):  
I. A. Shershan ◽  
T. V. Shishkina
Keyword(s):  
Standard Model ◽  
Gauge Boson ◽  
Cross Sections ◽  
Dimensional Regularization ◽  
High Energy ◽  
New Physics ◽  
Boson Production ◽  
Leading Order ◽  
The Standard Model ◽  
Electron Photon

Differential and total cross sections of single gauge boson production in high energy electron-photon collisions obtained within the Standard Model in leading order and next-to-leading order are presented. Soft photon bremsstrahlung as well as hard photon bremsstrahlung parts were considered using the dimensional regularization procedure. Special features of receiving the hard bremsstrahlung convergent contribution are discussed. The corresponding anomalous gauge boson couplings were studied in the effective Lagrangian approach. Best conditions for registration of effects beyond the Standard Model are determined.

scholarly journals Feynman Rules, Ward Identities and Loop Corrections in Very Special Relativity Standard Model

Universe ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 16 ◽  
Author(s):  
Jorge Alfaro
Keyword(s):  
Standard Model ◽  
Special Relativity ◽  
Effective Action ◽  
Dimensional Regularization ◽  
External Momentum ◽  
Ward Identities ◽  
Feynman Rules ◽  
Very Special Relativity ◽  
Charged Leptons ◽  
The Masses

In this paper, we want to study one loop corrections in Very Special Relativity Standard Model(VSRSM). In order to satisfy the Ward identities and the S i m ( 2 ) symmetry of the model, we have to specify the Feynman rules, including the infrared regulator. To do this, we adapt the Mandelstam–Leibbrandt (ML) prescription to incorporate external momentum-dependent null vectors. As an example, we use the new S i m ( 2 ) invariant dimensional regularization to compute one loop corrections to the effective action in the subsector of the VSRSM that describe the interaction of photons with charged leptons. New stringent bounds for the masses of ν e and ν μ are obtained.

Sign in / Sign up

Export Citation Format

Share Document