Recent observations from the DESI Collaboration indicate a preference for quintom dark energy, i.e., its equation of state evolves across the cosmological constant boundary $$w=-1$$ . It is well known that models with single perfect fluid or single scalar field minimally coupled to Einstein gravity develop perturbative instabilities around the crossing, thereby cannot realize the quintom scenario. In this paper, we propose a method to circumvent the instability problem of these models by considering the coupling of dark energy to the Nieh–Yan density within the framework of teleparallel gravity. We show that with this coupling the background evolution is not affected, but the dark energy perturbation is removed from the menu of dynamical degrees of freedom, thus avoiding the inherent difficulties in the old models. Furthermore, the Nieh–Yan coupling causes parity violation in gravitational waves, and this can be considered as a clear prediction of this mechanism.

China

Yuxuan Kang

Mingzhe Li

Changzhi Yi

Realization of quintom dark energy after DESI DR2 in Nieh–Yan modified teleparallel gravity

We perform a complete calculation of the next-to-next-to-leading order (NNLO) electroweak fermionic corrections to fermion-pair production processes, where “fermionic” refers to contributions with closed fermion loops. We do this via a semi-numerical technique that uses dispersion relations for the fermion sub-loop in two-loop box and vertex diagrams and dispersion relations and Feynman parameters for vertex diagrams with fermionic triangle sub-loops. UV and IR divergences are treated with suitable subtraction terms. We present numerical results for the cross-sections of $$ {e}^{+}{e}^{-}\to {\mu}^{+}{\mu}^{-}/u\overline{u}/d\overline{d} $$ and differential distributions at representative center-of-mass energies. The NNLO corrections are found to modify the NLO cross-section on the order of 1%.

United States

Ayres Freitas

E. Wallace

Fermionic electroweak two-loop corrections to Drell-Yan and related processes

<p>The Fermilab E906/SeaQuest collaboration performed measurements of the Drell-Yan process using 120 GeV proton beams bombarding liquid hydrogen and liquid deuterium targets. A combined analysis of all collected data was performed to obtain the final results for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>σ</mi><mrow><mi>p</mi><mi>d</mi></mrow></msub><mo>/</mo><mn>2</mn><msub><mi>σ</mi><mrow><mi>p</mi><mi>p</mi></mrow></msub></math> Drell-Yan cross section ratio covering the kinematic region of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.13</mn><mo>&lt;</mo><mi>x</mi><mo>&lt;</mo><mn>0.45</mn></math>. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math> dependencies of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mover accent="true"><mrow><mi>d</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow><mo>/</mo><mover accent="true"><mrow><mi>u</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>d</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow><mo>−</mo><mover accent="true"><mi>u</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></math> are extracted from these cross section ratios. It is found that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>d</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></math> is greater than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>u</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></math> over the entire measured <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math> range, with improved statistical accuracy compared to previous measurements. The new results on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>d</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow><mo>/</mo><mover accent="true"><mi>u</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>d</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow><mo>−</mo><mover accent="true"><mi>u</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></math> are compared to various parton distribution functions and theoretical calculations.</p>

C.H. Leung

J. Dove

Taiwan

Japan

K. Nagai

K. Nakano

S. Prasad

A.S. Tadepalli

C.A. Aidala

J. Arrington

C. Ayuso

C.L. Barker

W.C. Chang

A. Chen

D.C. Christian

B.P. Dannowitz

L. El Fassi

D.F. Geesaman

R. Gilman

Y. Goto

R.S. Guo

L. Guo

T.J. Hague

R.J. Holt

M.F. Hossain

L.D. Isenhower

E.R. Kinney

A. Klein

D. Kleinjan

P.J. Lin

K. Liu

M.X. Liu

W. Lorenzon

R.E. McClellan

P.L. McGaughey

M.M. Medeiros

Y. Miyachi

S. Miyasaka

D.H. Morton

K. Nakahara

J.C. Peng

A.J.R. Puckett

A. Pun

B.J. Ramson

P.E. Reimer

J.G. Rubin

F. Sanftl

S. Sawada

T. Sawada

M.B.C. Scott

T.A. Shibata

D.S. Su

M. Teo

R. Towell

S. Uemura

S.G. Wang

J. Wu

N. Wuerfel

Z.H. Ye

Final SeaQuest Results on the Flavor Asymmetry of the Proton Light-Quark Sea with Proton-Induced Drell-Yan Process

<p>We propose the “naive” <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>-odd Collins-Soper moments in the Drell-Yan process as probes of previously unexplored directions in the Standard Model effective field theory (SMEFT) parameter space. We show that the moments <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mn>6</mn></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mn>7</mn></msub></math> in the high invariant mass and transverse momentum region are sensitive to dimension-8 <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-odd semileptonic four-fermion operators with an additional gluon field strength tensor. Using the projected integrated luminosity of a future high-luminosity LHC, we show that effective ultraviolet scales in the few-TeV range can be probed with this process.</p>

Frank Petriello

Kaan Şimşek

Naive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>-odd Drell-Yan angular coefficients as a probe of the dimension-8 SMEFT

In this paper we present the first application of the MiNLO method to the calculation of QED NLO corrections to the production of a neutral vector boson in Drell–Yan processes. We consider only the case of initial-state radiation, when the $\textit{Z}$ boson decays into neutrinos. We illustrate the abelianization procedure of the MiNLO formulae and discuss the impact that it has on the differential cross section. We then propose a variant of the MiNLO formulae in order to circumvent some of the problems that arise when dealing with QED emissions. Since this is a case study, we use ad-hoc parton distribution functions and a larger value of the electromagnetic coupling constant, in order to emphasize potential discrepancies with respect to the expected behavior of the MiNLO formulae. We quantify the uncertainties connected with the proposed method, also for a physical value of the electromagnetic coupling. The study presented here is a necessary first step towards incorporating full electroweak effects into the $$\text {MiNNLO}_{\text {PS}}$$ framework.

Italy

Filippo Belloni

Mauro Chiesa

Carlo Oleari

Emanuele Re

Towards the inclusion of NLO EW corrections in the MiNLO method in Drell–Yan processes: the QED case

A striking prediction of QCD on the properties of the novel Transverse Momentum Dependent (TMD) distribution functions is that the time-reversal odd Sivers and Boer-Mulders functions extracted from semi-inclusive deep-inelastic scattering (SIDIS) will undergo a sign reversal in the Drell-Yan (DY) process. This prediction has been tested by experiments that have focused on the Sivers functions so far. We review the current status on the theoretical prediction and experimental extraction of the signs of the Boer-Mulders functions from SIDIS and DY. We note that the existing SIDIS and DY data are consistent with the predicted sign reversal of the Boer-Mulders functions for proton’s valence quark distribution. Prospects for future experiments at EIC capable of testing the sign reversal of the pion Boer-Mulders functions are also discussed.

Jen-Chieh Peng

Ming-Xiong Liu

Guanghua Xu

Sign reversal of Boer-Mulders functions from semi-inclusive deep-inelastic scattering to the Drell-Yan process

We study one-loop QCD corrections to the single transverse spin asymmetry in Drell-Yan process. The invariant mass of virtual photon and angular distributions of final lepton in Collins-Soper frame are measured. Especially, the transverse momentum of virtual photon is integrated out. Collinear twist-3 factorization formalism is adopted for the asymmetry. We use Feynman gauge in this work. To eliminate dependent twist-3 distribution functions, equation of motion for quark is used. The results satisfy both QED and QCD gauge invariance. It is confirmed that all divergences from virtual and real corrections can be removed consistently by collinear subtraction. Finite hard coefficients for the convolution of $$ \overline{q}(x) $$ and $\textit{T}$ ($\textit{x}$ , $\textit{x}$ ) are presented.

Guang-Peng Zhang

One-loop QCD corrections to SSA in unweighted Drell-Yan processes

We present a thorough investigation of the sources of uncertainties to the Drell-Yan production using state-of-the-art predictions for both neutral and charged current channels, focusing on the low invariant mass region. Differential predictions for the invariant mass spectrum are provided at N LO supplemented with exact charm and bottom quark mass effects calculated at $$ \mathcal{O}\left({\alpha}_s^2\right) $$ . The impact of PDF choices (including approximate N LO), scale variations, the variation of the strong coupling constant, and impact heavy quark mass effects on the distributions is studied in detail. We also comment on the correlation of high-energy astrophysical processes with the low-mass DY region.

Germany

Ekta Chaubey

Claude Duhr

Rhorry Gauld

Pooja Mukherjee

A comprehensive analysis of Drell-Yan production uncertainties and mass effects at moderate and low dilepton masses

In this paper, we present three types of teleparallel frames with cylindrical and spherical symmetry. The first example is the closed time-like curves (CTC) in cosmic strings in teleparallel $$T_{4}$$ gravity, which shows they are forbidden. Here, we show that in $$T_{4}$$ , in order to allow for CTC, we are also led to a lower bound on the angular momentum of the cosmic string. This result matches the interior $$T_{4}$$ solution to a General Relativity (GR) vacuum solution. One of the main differences between the present report and the one by Soleng is that, here, the interior symmetric solution does not have polarized spins but only Cartan torsion in the spirit of teleparallelism. Torsion flux is computed to show that a cylindrical central singularity corresponds to a $$(2+1)$$ -spacetime rotating point particle in $$T_{4}$$ . Therefore, the possibility of building time machines seems to be strongly constrained compared with Einstein–Cartan (EC) gravity. We present a spherically symmetric black hole with an open string along a particular direction of the black hole (BH). In this case, it is shown that when the teleparallel frame used is the one where all spin coefficients vanish, a torsion flux cutoff appears along one of the directions. In the stringy BH case, choosing a restricted teleparallel frame, a torsion-axion-like hair appears in the form of an axion scalar. A Kerr Nieh–Yan (NY) invariant black hole is obtained. Coley et al. previously obtained BH solutions in teleparallel spacetime, which present horizon singularities but not torsion singularities.

Brazil

Croatia

L. Garcia de Andrade

Strings in Gödel CTC and in hairy axionic black holes with Kerr Nieh–Yan charges in teleparallelism

We present results from a global fit of Standard Model parameters and dimension-6 SMEFT Wilson coefficients that includes electroweak, Drell-Yan, Higgs-boson, top-quark, and flavour observables. Fits obtained by floating individual coefficients are also discussed. The leading-order scale dependence of the SMEFT Wilson coefficients is consistently included in the evolution from the UV scale to the electroweak scale and the low-energy scale of flavour observables. In defining the SMEFT set of active operators we consider both the U(3) and the U(2) flavour symmetric limits. All fits are obtained within the HEPfit framework and are based on the most recent experimental results and state-of-the-art theoretical predictions for all the observables considered.

Spain

Jorge Blas

Angelica Goncalves

United Kingdom

Víctor Miralles

Laura Reina

Luca Silvestrini

Mauro Valli

Constraining new physics effective interactions via a global fit of electroweak, Drell-Yan, Higgs, top, and flavour observables