scholarly journals N-jettiness in electroweak high-energy processes

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Junegone Chay ◽  
Taewook Ha ◽  
Taehyun Kwon
Keyword(s):  
High Energy ◽  
Hard Scattering ◽  
Initial State ◽  
Final State ◽  
High Energies ◽  
State Radiation ◽  
The Standard Model ◽  
Energy Processes ◽  
Effective Theories ◽  
Logarithmic Accuracy

Abstract We study N-jettiness in electroweak processes at extreme high energies, in which the mass of the weak gauge bosons can be regarded as small. The description of the scattering process such as e−e+ → μ−μ+ + X is similar to QCD. The incoming leptons emit initial-state radiation and the resultant particles, highly off-shell, participate in the hard scattering, which are expressed by the beam functions. After the hard scattering, the final- state leptons or leptonic jets are observed, described by the fragmenting jet functions or the jet functions respectively. At present, electroweak processes are prevailed by the processes induced by the strong interaction, but they will be relevant at future e−e+ colliders at high energy. The main difference between QCD and electroweak processes is that the initial- and final-state particles should appear in the form of hadrons, that is, color singlets in QCD, while there can be weak nonsinglets as well in electroweak interactions. We analyze the factorization theorems for the N-jettiness in e−e+ → μ−μ+ + X, and compute the factorized parts to next-to-leading logarithmic accuracy. To simplify the comparison with QCD, we only consider the SU(2)W gauge interaction, and the extension to the Standard Model is straightforward. Put it in a different way, it corresponds to an imaginary world in which colored particles can be observed in QCD, and the richer structure of effective theories is probed. Various nonzero nonsinglet matrix elements are interwoven to produce the factorized results, in contrast to QCD in which there are only contributions from the singlets. Another distinct feature is that the rapidity divergence is prevalent in the contributions from weak nonsinglets due to the different group theory factors between the real and virtual corrections. We verify that the rapidity divergence cancels in all the contributions with a different number of nonsinglet channels. We also consider the renormalization group evolution of each factorized part to resum large logarithms, which are distinct from QCD.

scholarly journals Sensitivity of future linear $$\hbox {e}^+\hbox {e}^-$$ colliders to processes of dark matter production with light mediator exchange

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Jan Kalinowski ◽  
Wojciech Kotlarski ◽  
Krzysztof Mȩkała ◽  
Paweł Sopicki ◽  
Aleksander Filip Żarnecki
Keyword(s):  
Dark Matter ◽  
Linear Collider ◽  
Production Cross ◽  
Photon Emission ◽  
International Linear Collider ◽  
High Energy ◽  
Initial State ◽  
Final State ◽  
State Radiation ◽  
Wide Range

AbstractAs any $$e^+e^-$$ e + e - scattering process can be accompanied by a hard photon emission from the initial state radiation, the analysis of the energy spectrum and angular distributions of those photons can be used to search for hard processes with an invisible final state. Thus high energy $$e^+e^-$$ e + e - colliders offer a unique possibility for the most general search of dark matter (DM) based on the mono-photon signature. We consider production of DM particles at the International Linear Collider (ILC) and Compact Linear Collider (CLIC) experiments via a light mediator exchange. Detector effects are taken into account within the Delphes fast simulation framework. Limits on the light DM production in a simplified model are set as a function of the mediator mass and width based on the expected two-dimensional distributions of the reconstructed mono-photon events. The experimental sensitivity is extracted in terms of the DM production cross section. Limits on the mediator couplings are then presented for a wide range of mediator masses and widths. For light mediators, for masses up to the centre-of-mass energy of the collider, coupling limits derived from the mono-photon analysis are more stringent than those expected from direct resonance searches in decay channels to SM particles.

scholarly journals Initial state radiation in the Herwig 7 angular-ordered parton shower

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Gavin Bewick ◽  
Silvia Ferrario Ravasio ◽  
Peter Richardson ◽  
Michael H. Seymour
Keyword(s):  
Parton Shower ◽  
Phenomenological Study ◽  
Initial State Radiation ◽  
Centre Of Mass ◽  
Initial State ◽  
Final State ◽  
State Radiation ◽  
Optimal Values ◽  
Logarithmic Accuracy ◽  
Intrinsic Transverse Momentum

Abstract We study the simulation of initial-state radiation in angular-ordered parton showers in order to investigate how different interpretations of the ordering variable affect the logarithmic accuracy of such showers. This also enables us to implement a recoil scheme which is consistent between final-state and initial-state radiation. We present optimal values of the strong coupling and intrinsic transverse momentum to be used in each version of the parton shower, tuned using Z0-boson production at the LHC at 7 TeV. With these tuned showers, we perform a phenomenological study of the Drell-Yan process at several centre-of-mass energies.

scholarly journals Suppression of electroweak instanton processes in high-energy collisions

2021 ◽  
pp. 2150032
Author(s):  
Valentin V. Khoze ◽  
Daniel L. Milne
Keyword(s):  
Cross Section ◽  
Production Cross ◽  
High Energy ◽  
Optical Theorem ◽  
Initial State ◽  
The Past ◽  
The Standard Model ◽  
Low Energies ◽  
High Energy Collisions ◽  
High Energy Regime

Electroweak instantons are a prediction of the Standard Model and have been studied in great detail in the past although they have not been observed. Earlier calculations of the instanton production cross-section at colliders revealed that it was exponentially suppressed at low energies, but may grow large at energies (much) above the sphaleron mass. Such calculations faced difficulty in the breakdown of the instanton perturbation theory in the high-energy regime. In this paper, we review the calculation for the electroweak instanton cross-section using the optical theorem, including quantum effects arising from interactions in the initial state and show that this leads to an exponential suppression of the cross-section at all energies, rendering the process unobservable.

scholarly journals Latest studies on the reaction e+e− → K+K−γ

2018 ◽  
Vol 166 ◽  
pp. 00018 ◽  
Author(s):  
Leonard Leśniak ◽  
Michał Silarski
Keyword(s):  
Reaction Mechanisms ◽  
Initial State Radiation ◽  
Main Reaction ◽  
Theoretical Studies ◽  
Initial State ◽  
Final State ◽  
Mass Distributions ◽  
Radiative Processes ◽  
Pseudoscalar Mesons ◽  
State Radiation

Recent theoretical studies of the e+e- → K+K-γ process are described. Three main reaction mechanisms are considered: the initial state radiation, the final state radiation and the strong interaction between the outgoing K+K- mesons. The K+K- effective mass distributions are derived for three different models which in past have been used for a description of the e+e- → π+π-η data. Also the numerical results for the angular photon and kaon distributions are presented. A new model of the e+e- → M1M2γ reactions is outlined which can serve for multichannel analyses of the radiative processes with a production of two pseudoscalar mesons M1 and M2.

scholarly journals Measurement of initial-state–final-state radiation interference in the processese+e−→μ+μ−γande+e−→π+π−γ

2015 ◽  
Vol 92 (7) ◽  
Author(s):  
J. P. Lees ◽  
V. Poireau ◽  
V. Tisserand ◽  
E. Grauges ◽  
A. Palano ◽  
...  
Keyword(s):  
Initial State ◽  
Final State ◽  
Final State Radiation ◽  
State Radiation

scholarly journals From Hadronic Cross Section to the measurement of the Vacuum Polarization at KLOE: a fascinating endeavour

2018 ◽  
Vol 166 ◽  
pp. 00021 ◽  
Author(s):  
Graziano Venanzoni
Keyword(s):  
Standard Model ◽  
Cross Section ◽  
Vacuum Polarization ◽  
Direct Determination ◽  
Initial State Radiation ◽  
Initial State ◽  
Hadronic Cross Section ◽  
State Radiation ◽  
The Standard Model

The KLOE experiment at the ϕ-factory DAΦNE in Frascati is the first to have employed Initial State Radiation (ISR) to precisely determine the e+e− → π+π−(γ) cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the (g – 2) of the muon, where a long standing 3σ discrepancy is observed. I will review the ISR activity in KLOE in the last 20 years from the measurement of the hadronic cross section to the first direct determination of the time-like complex running α(s) in the region below 1 GeV.

MEASUREMENT OF THE HADRONIC CROSS SECTION AT KLOE/KLOE-2

2014 ◽  
Vol 35 ◽  
pp. 1460389
Author(s):  
ANTHONY PALLADINO ◽  
Keyword(s):  
Cross Section ◽  
Collision Energy ◽  
Large Angle ◽  
Pion Form Factor ◽  
Initial State ◽  
Hadronic Cross Section ◽  
Bhabha Scattering ◽  
State Radiation ◽  
The Standard Model ◽  
Using Data

The KLOE experiment at the DAΦNE ϕ-factory in Frascati was the first to use Initial State Radiation to precisely determine the e+e− → π+π−(γ) cross section below 1 GeV. This measurement is particularly important to test the Standard Model calculation for the anomalous magnetic moment of the muon, (g-2), where a long standing 3σ discrepancy between measurement and theory is observed. In 2005 and 2008 KLOE published two measurements of the π+π− cross section with the photon emitted at small angle. In 2011 an independent measurement of the π+π− cross section with the photon emitted at large angle was published using data at a collision energy of 1 GeV, 20 MeV below the ϕ-peak. A new analysis, published in 2013, derives the pion form factor directly from the bin-by-bin π+π−γ/μ+μ−γ ratio significantly reducing the systematic uncertainty, while the previous measurements were normalized to the DAΦNE luminosity using large angle Bhabha scattering. We present the final result of this measurement, as well as a preliminary value for the combined result of all KLOE hadronic cross section measurements, and evaluate the hadronic contribution to the muon anomaly.

scholarly journals Experimental Review of ΛΛ¯ Production

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 144
Author(s):  
Xiaorong Zhou ◽  
Liang Yan ◽  
Rinaldo Baldini Ferroli ◽  
Guangshun Huang
Keyword(s):  
Positron Annihilation ◽  
Cross Section ◽  
Production Cross ◽  
High Energy ◽  
Threshold Region ◽  
Initial State ◽  
Precision Data ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
State Radiation

Exclusive hyperon-antihyperon production provides a unique insight for understanding of the intrinsic dynamics when strangeness is involved. In this paper, we review the results of ΛΛ¯ production via different reactions from various experiments, e.g., via p¯p annihilation from the LEAR experiment PS185, via electron-positron annihilation using the energy scan method at the CLEO-c and BESIII experiments and the initial-state-radiation approach utilized at the BaBar experiment. The production cross section of ΛΛ¯ near the threshold is sensitive to QCD based prediction. Experimental high precision data for p¯p→Λ¯Λ close to the threshold region is obtained. The cross section of e+e−→ΛΛ¯ is measured from its production threshold to high energy. A non-zero cross section for e+e−→ΛΛ¯ near threshold is observed at BaBar and BESIII, which is in disagreement with the pQCD prediction. However, more precise data is needed to confirm this observation. Future experiments, utilizing p¯p reaction such as PANDA experiment or electron-positron annihilation such as the BESIII and BelleII experiments, are needed to extend the experimental data and to understand the ΛΛ¯ production.

SOFT PHOTON RADIATION IN $e^+ e^- \to t\bar t\to b\bar bW^+ W^-$

1993 ◽  
Vol 08 (13) ◽  
pp. 1191-1204 ◽  
Author(s):  
G. F. ABU LEIL
Keyword(s):  
Radiation Pattern ◽  
Relative Orientation ◽  
Initial State Radiation ◽  
Soft Photon ◽  
Photon Radiation ◽  
Optimum Conditions ◽  
Initial State ◽  
Final State ◽  
State Radiation ◽  
Top Mass

We present a detailed analysis of soft photon radiation in [Formula: see text]. The radiation pattern is shown to depend sensitively on the top mass, width and energy, as well as the relative orientation of the initial and final state particles. Optimum conditions in which initial state radiation is minimized and the radiation pattern has the richest structure are discussed.

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