Yan Process Research Articles

Composite dark matter and neutrino masses from a light hidden sector

We study a class of models in which the particle that constitutes dark matter arises as a composite state of a strongly coupled hidden sector. The hidden sector interacts with the Standard Model through the neutrino portal, allowing the relic abundance of dark matter to be set by annihilation into final states containing neutrinos. The coupling to the hidden sector also leads to the generation of neutrino masses through the inverse seesaw mechanism, with composite hidden sector states playing the role of the singlet neutrinos. We focus on the scenario in which the hidden sector is conformal in the ultraviolet, and the compositeness scale lies at or below the weak scale. We construct a holographic realization of this framework based on the Randall-Sundrum setup and explore the implications for experiments. We determine the current constraints on this scenario from direct and indirect detection, lepton flavor violation and collider experiments and explore the reach of future searches. We show that in the near future, direct detection experiments and searches for μ → e conversion will be able to probe new parameter space. At colliders, dark matter can be produced in association with composite singlet neutrinos via Drell Yan processes or in weak decays of hadrons. We show that current searches at the Large Hadron Collider have only limited sensitivity to this new production channel and we comment on how the reconstruction of the singlet neutrinos can potentially expand the reach.

Impact of Higher-Order QCD Effects on Angular Polarization Coefficients in the Drell–Yan Process at the LHC

Impact of Higher-Order QCD Effects on Angular Polarization Coefficients in the Drell–Yan Process at the LHC

Determination of the strong-coupling constant from the Z-boson transverse-momentum distribution

The strong-coupling constant is determined from the low-momentum region of the transverse-momentum distribution of Z bosons produced through the Drell–Yan process, using predictions at third order in perturbative QCD. The analysis employs a measurement performed in proton-antiproton collisions at a centre-of-mass energy of s=1.96\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 1.96$$\\end{document} TeV with the CDF experiment. The determined value of the strong coupling at the reference scale corresponding to the Z-boson mass is αS(mZ)=0.1191-0.0016+0.0013\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _S(m_Z)= 0.1191^{+0.0013}_{-0.0016}$$\\end{document}.

Global extraction of proton and pion Transverse Momentum Distributions

We present the most recent global analysis of unpolarized proton Transverse Momentum Dependent Parton Distribution Functions (TMD PDFs) and Fragmentation Functions (TMD FFs) derived from a diverse set of experimental datasets, including Semi-Inclusive Deep-Inelastic Scattering, Drell-Yan, and Z-boson production. Additionally, we present an extraction of the unpolarized pion TMD PDFs from all available data of unpolarized pion induced Drell–Yan processes. Both fits are performed at next-to-next-to-next-to-leading logarithmic (N3LL) accuracy.

Determination of the W-boson mass at hadron colliders

We introduce an observable relevant for the determination of the W-boson mass mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} at hadron colliders. This observable is defined as an asymmetry around the jacobian peak of the charged-lepton transverse-momentum distribution in the charged-current Drell–Yan process. We discuss the observable’s theoretical prediction, presenting results at different orders in QCD, and showing its perturbative stability. Its definition as a single scalar number and its linear sensitivity to mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} allow a clean extraction of the latter and a straightforward discussion of the associated theoretical systematics: a perturbative QCD uncertainty of O(±5)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{\\mathcal {O}}}}(\\pm 5)$$\\end{document} MeV on mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} can be established by means of this observable, relying solely on charged-current Drell–Yan information. Owing to its relatively inclusive nature, the observable displays desirable properties also from the experimental viewpoint, especially for the unfolding of detector effects. We show that a measurement of this observable can lead to a competitive experimental error on mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} at the LHC.

Search for resonant WZ production in the fully leptonic final state in proton–proton collisions at mathbf {sqrt{s} = 13} TeV with the ATLAS detector

A search for a WZ resonance, in the fully leptonic final state (electrons or muons), is performed using 139 fb^{-1} of data collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The results are interpreted in terms of a singly charged Higgs boson of the Georgi–Machacek model, produced by WZ fusion, and of a Heavy Vector Triplet, with the resonance produced by WZ fusion or the Drell–Yan process. No significant excess over the Standard Model prediction is observed and limits are set on the production cross-section times branching ratio as a function of the resonance mass for these processes.

Electroweak Effects in Neutral Current Drell–Yan Processes within SANC System

Electroweak Effects in Neutral Current Drell–Yan Processes within SANC System

Hunting for an EMC–like effect for antiquarks

We argue that the Drell–Yan process in the xA≥0.15 kinematics recently studied at FNAL by the E906/SeaQuest experiment may allow to observe an analogous of the EMC effect for antiquarks. The effects of Fermi motion and energy loss are considered. The preliminary E906/SeaQuest data are inconsistent with the growth of the σA/AσN ratio expected in the Fermi motion scenario at xA≥0.25. The pattern of the xA dependence of the ratio seems also inconsistent with a scenario in which the dominant nuclear effect is a suppression of the cross section due to the energy loss experienced by a quark of the projectile proton involved in the Drell–Yan process. All together the data suggest the possibility of a modification of the antiquark parton distributions in nuclei, with a pattern similar to the one observed in the EMC effect. We argue that optimal kinematics to look for an antiquark EMC–like effect would be to measure the σADY/AσNDY ratios for xA = 0.2 – 0.4 and xp ≈ constant.

Exclusive doubly charged Higgs boson pair production in pp collisions at the LHC

The type II seesaw model predicts the existence of a doubly charged Higgs boson ($H ^{\pm\pm}$), which can be produced through the Drell - Yan process and photon -- induced interactions at hadronic colliders. In recent years, such reactions have been largely investigated in inclusive processes, where both incident protons breakup and a large number of particles is produced in addition to the doubly charged Higgs pair. In this paper, we investigate, for the first time, the possibility of searching for $H ^{\pm\pm}$ in exclusive processes, which are characterized by two rapidity gaps and two intact very forward protons in final state. We estimate the associated cross section making use of the exclusive nature of the final state, together with the use of timing information provided by forward proton detectors. Moreover, the background is estimated considering distinct amounts of pile-up. Our results indicate that the exclusive doubly charged Higgs pair production is a promising way to search for signatures of the type II seesaw and to obtain lower mass bounds on $H ^{\pm\pm}$.

Precision studies for string derived Z' dynamics at the LHC

We consider Z's in heterotic string derived models and study Z' resonant production at the TeV scale at the Large Hadron Collider (LHC). We use various kinematic differential distributions for the Drell–Yan process at NNLO in QCD to explore the parameter space of such models and investigate Z' couplings. In particular, we study the impact of Z-Z' kinetic-mixing interactions on forward-backward asymmetry (A_{FB}) and other distributions at the LHC.

Extraction of pion transverse momentum distributions from Drell-Yan data

We map the distribution of unpolarized quarks inside a unpolarized pion as a function of the quark's transverse momentum, encoded in unpolarized transverse momentum distributions (TMDs). We extract the pion TMDs from available data of unpolarized pion-nucleus Drell--Yan processes, where the cross section is differential in the lepton-pair transverse momentum. In the cross section, pion TMDs are convoluted with nucleon TMDs that we consistently take from our previous studies. We obtain a fairly good agreement with data. We present also predictions for pion-nucleus scattering that is being measured by the COMPASS Collaboration.

Resolving muon g-2 anomaly with partial compositeness

We consider the scenario of composite Higgs with partial compositeness to address the muon g-2 anomaly. We show that this anomaly is resolved by one-loop correction due to composite muon partners with mass scale of order TeVs and large Yukawa coupling to composite Higgs, which is different from interpretations of vectorlike lepton models. We present parameter space by imposing indirect constraints from precise measurements on Higgs, Z and oblique electroweak parameters. We analyze direct constraints in light of both Drell–Yan and Higgs-associated productions of the composite muon partners at high-luminosity LHC. It turns out that the parameter regions with the lighter composite muon mass below sim 325 GeV can be excluded at 2sigma order by the Drell–Yan processes.

Reduction of the electroweak correlation in the PDF updating by using the forward–backward asymmetry of Drell–Yan process

We propose a new observable for the measurement of the forward–backward asymmetry (A_{FB}) in Drell–Yan lepton production. At hadron colliders, the A_{FB} distribution is sensitive to both the electroweak (EW) fundamental parameter sin ^{2} theta _{W}, the weak mixing angle, and the parton distribution functions (PDFs). Hence, the determination of sin ^{2} theta _{W} and the updating of PDFs by directly using the same A_{FB} spectrum are strongly correlated. This correlation would introduce large bias or uncertainty into both precise measurements of EW and PDF sectors. In this article, we show that the sensitivity of A_{FB} on sin ^{2} theta _{W} is dominated by its average value around the Z pole region, while the shape (or gradient) of the A_{FB} spectrum is insensitive to sin ^{2} theta _{W} and contains important information on the PDF modeling. Accordingly, a new observable related to the gradient of the spectrum is introduced, and demonstrated to be able to significantly reduce the potential bias on the determination of sin ^{2} theta _{W} when updating the PDFs using the same A_{FB} data.

An effective field theory treatment of the production and annihilation of magnetic monopoles and their relic abundance

We revisit the thermal production and annihilation of magnetic monopoles and their relic abundance in order to gain a deeper physical interpretation on the monopole phenomenology predicted from the Baines et al.’s effective field theory, recently proposed in the description of monopole pair production via Drell–Yan and photon fusion processes. In this sense, we use of the vacuum cross sections for the Drell–Yan reactions derived within the mentioned framework to evaluate the cross section averaged over the thermal distribution associated to other particles that constitute the hot medium where the monopoles propagate. In the considered range of monopole mass with spin-zero and spin-half, our findings suggest that the thermally averaged cross sections for the pair production are highly suppressed, while at higher temperatures those for the annihilation of lighter pairs reach larger magnitudes. Besides, we observe that smaller temperature leads to a rate of annihilation for scalar monopoles smaller than the one for fermionic monopoles, which might be interpreted as a theoretical evidence of a more pronounced stability for spin-zero and heavier monopoles. Then we input these thermally averaged cross sections into the kinetic equation that describes the evolution of the monopole abundance via an extension of a freeze-out theory. Our results infer that heavier monopoles achieve the equilibrium at earlier stages of the expansion, and consequently at higher temperatures. In addition, larger monopole masses produce higher values of the relic abundance. Besides, the results indicate that the abundance does not behave differently for spin-zero and spin-half relic monopoles.

Probing Nucleon Spin Structure in Deep-inelastic Scattering, Proton–Proton Collisions, and Drell–Yan Processes

A pedagogical summary of current and past experimental results of spin-dependent nucleon structure prior to the arrival of the Electron-Ion Collider is attempted. After an introduction, results from fixed-target experiments at SLAC, Fermilab, Jefferson Lab, CERN and DESY and collider experiments from RHIC are presented, starting with the longitudinal spin structure of the nucleon, followed by generalized parton distributions (GPDs), which map the proton in transverse position space. The final part discusses transverse proton or parton spin and transverse parton momenta (TMDs), and their their (spin-orbit) correlations, which are addressed by a multitude of recent experimental results. The GPDs and TMDs provide complementary pathways to mapping multi-dimensional nucleon structure.

Measurement of Angular Coefficients in the Drell–Yan Process in the CMS Experiment at the LHC

Measurement of Angular Coefficients in the Drell–Yan Process in the CMS Experiment at the LHC

Effects of Radiative Corrections in the Drell–Yan Process at Ultrahigh Dilepton Invariant Masses

Effects of Radiative Corrections in the Drell–Yan Process at Ultrahigh Dilepton Invariant Masses

Boer\u2013Mulders function of the pion and pretzelosity distribution of the proton in the polarized pion-proton Drell\u2013Yan process at COMPASS

We present a phenomenological analysis of the q_{text {T}}-weighted transverse spin dependent azimuthal asymmetry recently measured by the COMPASS Collaboration in polarized pion-proton Drell–Yan process. In the kinematical regimes explored by experiments, we consider the leading-twist contributions from the Boer–Mulders distribution functions h_{1}^{perp }(x,k_{text {T}}^{2}) of both the pion and the proton, the transversity distribution h_{1}(x,k_{text {T}}^{2}) and the pretzelosity distribution h_{1text {T}}^{perp }(x,k_{text {T}}^{2}) of the proton, with the unpolarized transverse-momentum-dependent distribution function f_{1}(x,k_{text {T}}^{2}) of the proton being also involved in the calculation. By comparing the data reported by the COMPASS Collaboration with theoretical calculated results, we find that the COMPASS measurements represent the first experimental evidence of the Boer–Mulders effect in polarized Drell–Yan process. We also test the universality between proton and pion Boer–Mulders functions.

Precision studies for Drell\u2013Yan processes at NNLO

We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell–Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.

Bjorken variable and scale dependence of quark transport coefficient in Drell–Yan process for proton incident on nucleus

The Drell-Yan process for proton incident on nuclei is an excellent place for deeply studying the parton propagation in a nucleus. By means of the nuclear parton distributions determined only with lepton-nuclear deep inelastic scattering experimental data and the analytic parameterization of quenching weight based on BDMPS formalism, a phenomenological analysis of the nuclear Drell-Yan differential cross section ratio as a function of Feynman variable is performed from Fermilab E906 and E866 experimental data. With the nuclear geometry effect on nuclear Drell-Yan process and the quark transport coefficient as a constant, our predictions are in good agreement with the experimental measurements. It is found that nuclear geometry effect has a significant impact on the quark transport coefficient in cold nuclear matter. It is necessary to consider the detailed nuclear geometry in studying the nuclear Drell-Yan process. Our calculated results reveal that the difference in the values of quark transport coefficient exists from E906 and E866 experiments. However, confirming the conclusion that the quark transport coefficient depends on the target-quark momentum fraction, still need more accurate experimental data on the Drell-Yan differential cross section ratio in the future. Three models are proposed and discussed for the quark transport coefficient as a function of the measurable kinematic variables. The quark transport coefficient $\hat{q}$ is determined as a function of the Bjorken variable $x_2$ and scale $Q^2$. It is hoped that the parametrization form of quark transport coefficient in the cold nuclear medium can help to think about the parton propagation mechanism in nuclear matter.