scholarly journals High-energy γ -photon polarization in nonlinear Breit-Wheeler pair production and γ polarimetry

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Feng Wan ◽  
Yu Wang ◽  
Ren-Tong Guo ◽  
Yue-Yue Chen ◽  
Rashid Shaisultanov ◽  
...  
Keyword(s):  
Pair Production ◽  
High Energy ◽  
Photon Polarization

scholarly journals A CRITICAL LOOK AT PRECISION ELECTROWEAK DATA AT HIGH ENERGY—A HINT FOR PHYSICS BEYOND THE STANDARD MODEL?

1994 ◽  
Vol 09 (35) ◽  
pp. 3301-3312
Author(s):  
A. GURTU
Keyword(s):  
Standard Model ◽  
Pair Production ◽  
High Energy ◽  
Recent Measurement ◽  
Beyond The Standard Model ◽  
Full Data ◽  
Text Production ◽  
Basic Framework ◽  
The Standard Model ◽  
Precision Electroweak Data

High energy electroweak data, including the recent measurement of M top is analyzed within the basic framework of the standard model. While the experimentally measured value of [Formula: see text] implies a low value of M top , the rest of the data demands a much higher value. Estimates of M Higgs within the SM framework including and excluding this Rb measurement are given. Next this discrepancy is expressed in terms of a new parameter, [Formula: see text], the excess[Formula: see text] production compared to that expected from a SM fit. This parameter is determined to be (9.4 to 12.8) ± 5.0 MeV, implying an excess of over 10 000 [Formula: see text] events in each LEP experiment after the 1993 data is fully analyzed. The origin of these events could be non-minimal Higgs pair production which should be thoroughly searched for in the full data sample of ~2×106 events per LEP experiment. Unless this discrepancy eventually turns out to be a fluctuation one may be witnessing at LEP the advent of physics beyond the standard model.

scholarly journals Prompt $${J/\psi }$$-pair production at the LHC: impact of loop-induced contributions and of the colour-octet mechanism

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Jean-Philippe Lansberg ◽  
Hua-Sheng Shao ◽  
Nodoka Yamanaka ◽  
Yu-Jie Zhang
Keyword(s):  
Pair Production ◽  
Good Control ◽  
Distance Matrix ◽  
High Energy ◽  
Matrix Elements ◽  
Hadron Colliders ◽  
Long Distance ◽  
Gauge Invariant ◽  
Energy Hadron ◽  
Colour Octet

AbstractPrompt double-$$J/\psi $$J/ψ production at high-energy hadron colliders can be considered as a golden channel to probe double parton scatterings (DPS)—in particular to study gluon–gluon correlations inside the proton—and, at the same time, to measure the distribution of linearly-polarised gluons inside the proton. Such studies, however, require a good control of both single parton scatterings (SPS) and DPS in the respective regions where they are carried out. In this context, we have critically examined two mechanisms of SPS that may be kinematically enhanced where DPS are thought to be dominant, even though they are either at higher orders in the strong-coupling or velocity expansion. First, we have considered a gauge-invariant and infrared-safe subset of the loop-induced contribution via colour-singlet (CS) transitions. We have found it to become the leading CS SPS contributions at large rapidity separation, yet too small to account for the data without invoking the presence of DPS yields. Second, we have surveyed the possible colour-octet (CO) contributions using both old and up-to-date non-perturbative long-distance matrix elements (LDMEs). We have found that the pure CO yields crucially depend on the LDMEs. Among all the LDMEs we used, only two result into a visible modification of the NRQCD (CS+CO) yield, but only in two kinematical distributions measured by ATLAS, those of the rapidity separation and of the pair invariant mass. These modifications, however, do not impact the control region used for their DPS study.

scholarly journals Electron Pair Production at High Energy in a Silicon Single Crystal

1960 ◽  
Vol 4 (3) ◽  
pp. 134-135 ◽  
Author(s):  
G. Bologna ◽  
G. Diambrini ◽  
G. P. Murtas
Keyword(s):  
Single Crystal ◽  
Pair Production ◽  
Electron Pair ◽  
High Energy ◽  
Silicon Single Crystal

scholarly journals The production of charged-kaon pairs in proton–antiproton collisions: The role of higher-twist mechanism

2018 ◽  
Vol 33 (28) ◽  
pp. 1850166 ◽  
Author(s):  
M. Demirci ◽  
A. I. Ahmadov
Keyword(s):  
Transverse Momentum ◽  
Pair Production ◽  
Quark Model ◽  
Inclusive Cross Section ◽  
Gluon Fusion ◽  
High Energy ◽  
Light Front ◽  
Charged Kaon ◽  
Proton Antiproton ◽  
Direct Production

The higher-twist (HT) contribution to the charged-kaon pair production in the high energy proton–antiproton collisions at large transverse momentum [Formula: see text] is investigated by using the frozen coupling constant approach for various kaon distribution amplitudes (DAs), which are predicted by light-cone formalism, the light-front quark model, the nonlocal chiral quark model and the light-front holographic AdS/CFT approach. In the numerics, the dependencies of the HT contribution on the transverse momentum [Formula: see text], the rapidity [Formula: see text], and the variable [Formula: see text] are discussed with special emphasis put on DAs. The HT contribution is also compared with the leading-twist ones. It is shown that the HT contributions are dependent on the kaon DAs and also some other phenomenological parameters such as momentum cutoff parameter [Formula: see text]. Inclusive kaon pair production presents a remarkable test case in which HT terms dominate those of LT in certain kinematic regions. The HT direct production process via gluon–gluon fusion contributes significantly to the inclusive cross-section at large [Formula: see text].

scholarly journals Resonant Ultrarelativistic Electron–Positron Pair Production by High-Energy Electrons in the Field of an X-ray Pulsar

Universe ◽  
2020 ◽  
Vol 6 (9) ◽  
pp. 132 ◽  
Author(s):  
Georgii K. Sizykh ◽  
Sergei P. Roshchupkin ◽  
Victor V. Dubov
Keyword(s):  
Pair Production ◽  
Threshold Energy ◽  
Structure Constant ◽  
High Energy ◽  
Differential Probability ◽  
X Ray ◽  
Initial Electron ◽  
Ultrarelativistic Electron ◽  
Electron Positron ◽  
Electron Positron Pair

The process of resonant high-energy electron–positron pair production by an ultrarelativistic electron colliding with the field of an X-ray pulsar is theoretically investigated. Resonant kinematics of the process is studied in detail. Under the resonance condition, the intermediate virtual photon in the X-ray pulsar field becomes a real particle. As a result, the initial process of the second order in the fine structure constant effectively reduces into two successive processes of the first order: X-ray-stimulated Compton effect and X-ray-stimulated Breit–Wheeler process. For a high-energy initial electron all the final ultrarelativistic particles propagate in a narrow cone along the direction of the initial electron momentum. The presence of threshold energy for the initial electron which is of order of 100 MeV for 1-KeV-frequency field is shown. At the same time, the energy spectrum of the final particles (two electrons and a positron) highly depends on their exit angles and on the initial electron energy. This result significantly distinguishes the resonant process from the non-resonant one. It is shown that the resonant differential probability significantly exceeds the non-resonant one.

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