scholarly journals Prompt $$J/\psi $$ photoproduction within the non-relativistic QCD framework at the CEPC

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Xi-Jie Zhan ◽  
Jian-Xiong Wang
Keyword(s):  
Transverse Momentum ◽  
Total Cross Section ◽  
Cross Section ◽  
Hadron Collider ◽  
Distance Matrix ◽  
Matrix Elements ◽  
Long Distance ◽  
Color Octet ◽  
Electron Positron ◽  
The Future

Abstract The prompt $$J/\psi $$J/ψ photoproduction within the non-relativistic QCD (NRQCD) framework at the future Circular Electron Positron Collider (CEPC) is studied, including the contributions from both direct and resolved photons. Employing different sets of long distance matrix elements, the total cross section is dominated by the color-octet channel. We present different kinematic distributions of $$J/\psi $$J/ψ production and the results show there will be about 50 $$J/\psi $$J/ψ events when the transverse momentum of $$J/\psi $$J/ψ is up to 20 GeV. It renders that the $$J/\psi $$J/ψ photoprodution at the CEPC is a well laboratory to test the NRQCD and further clarify the universality problem in NRQCD between electron positron collider and hadron collider.

scholarly journals $$\chi _{c1}$$ and $$\chi _{c2}$$ polarization as a probe of color octet channel

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
S. P. Baranov ◽  
A. V. Lipatov
Keyword(s):  
Bound States ◽  
Distance Matrix ◽  
Wave Functions ◽  
Color Singlet ◽  
Matrix Elements ◽  
Polarization Data ◽  
Long Distance ◽  
Factorization Approach ◽  
Color Octet ◽  
Polar Anisotropy

AbstractWe analyze joint LHC data on the production of $$\chi _{c1}$$ χ c 1 and $$\chi _{c2}$$ χ c 2 mesons together with the polarization data obtained very recently by the CMS Collaboration at $$\sqrt{s} = 8$$ s = 8  TeV. Our consideration is based on the $$k_T$$ k T -factorization approach and nonrelativistic QCD formalism for the formation of bound states. The observed polar anisotropy of $$\chi _{c1}$$ χ c 1 and $$\chi _{c2}$$ χ c 2 decays can be described as a combined effect of the color-singlet and color-octet contributions. We extract the corresponding long-distance matrix elements from the fits. Our fits point to unequal color singlet wave functions for $$\chi _{c1}$$ χ c 1 and $$\chi _{c2}$$ χ c 2 states.

Bc → J/ψ tensor form factors at large momentum recoil

2021 ◽  
pp. 2150135
Author(s):  
Dandan Shen ◽  
Huimin Ren ◽  
Fan Wu ◽  
Ruilin Zhu
Keyword(s):  
Form Factors ◽  
Distance Matrix ◽  
Relativistic Correction ◽  
Large Momentum ◽  
Matrix Elements ◽  
Leading Order ◽  
Lattice Data ◽  
Tensor Form ◽  
Long Distance ◽  
Current Form

We present a next-to-leading order (NLO) relativistic correction to [Formula: see text] tensor form factors within nonrelativistic QCD (NRQCD). We also consider complete Dirac bilinears [Formula: see text] with [Formula: see text] matrices [Formula: see text] in the [Formula: see text] transition. The relation among different current form factors is given and it shows that symmetries emerge in the heavy bottom quark limit. For a phenomenological extension, we propose to extract the long-distance matrix elements (LDMEs) for [Formula: see text] meson from the recent HPQCD lattice data and the NLO form factors at large momentum recoil.

scholarly journals H1jet, a fast program to compute transverse momentum distributions

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Alexander Lind ◽  
Andrea Banfi
Keyword(s):  
Transverse Momentum ◽  
Standard Model ◽  
Total Cross Section ◽  
Cross Section ◽  
New Physics ◽  
Leading Order ◽  
Current Version ◽  
Differential Distribution ◽  
The Standard Model ◽  
Momentum Distributions

AbstractWe present H1jet, a fast code that computes the total cross section and differential distribution in the transverse momentum of a colour singlet. In its current version, the program implements only leading-order $$2\rightarrow 1$$ 2 → 1 and $$2\rightarrow 2$$ 2 → 2 processes, but could be extended to higher orders. We discuss the processes implemented in H1jet, give detailed instructions on how to implement new processes, and perform comparisons to existing codes. This tool, mainly designed for theorists, can be fruitfully used to assess deviations of selected new physics models from the Standard Model behaviour, as well as to quickly obtain distributions of relevance for Standard Model phenomenology.

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 Quarkonium Production: Velocity-Scaling Rules and Long-Distance Matrix Elements

1997 ◽  
Vol 12 (22) ◽  
pp. 3951-3963 ◽  
Author(s):  
Gerhard A. Schuler
Keyword(s):  
Heavy Quark ◽  
Bound States ◽  
Potential Model ◽  
Distance Matrix ◽  
Bound State ◽  
Matrix Elements ◽  
Long Distance ◽  
Quarkonium Production ◽  
Quark Potential ◽  
Colour Octet

The hierarchy of long-distance matrix elements (MEs) for quarkonium production depends on their scaling with the velocity v of the heavy quark in the bound state. Ranges for the velocities in various bound states and uncertainties of colour-singlet MEs are estimated in a quark-potential model. Different possibilities for the scaling with v of the MEs are discussed; they depend on the actual values of v and the QCD scale. As an application, J/ψ polarization in e+e- annihilation is discussed. The first non-perturbative estimates of colour-octet MEs are presented and compared with phenomenological determinations. Finally, various predictions of prompt quarkonium production at LEP are compared.

scholarly journals Z′Resonance and AssociatedZhProduction at Future Higgs Boson Factory: ILC and CLIC

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
A. Gutiérrez-Rodríguez ◽  
M. A. Hernández-Ruíz
Keyword(s):  
Higgs Boson ◽  
Total Cross Section ◽  
Cross Section ◽  
Center Of Mass ◽  
High Energy ◽  
Precision Measurements ◽  
Linear Electron ◽  
High Luminosity ◽  
Electron Positron

We study the prospects of theB-Lmodel with an additionalZ′boson to be a Higgs boson factory at high-energy and high-luminosity linear electron positron colliders, such as the ILC and CLIC, through the Higgs-strahlung processe+e-→(Z,Z′)→Zh, including both the resonant and the nonresonant effects. We evaluate the total cross section ofZhand we calculate the total number of events for integrated luminosities of 500–2000 fb−1and center of mass energies between 500 and 3000 GeV. We find that the total number of expectedZhevents can reach 106, which is a very optimistic scenario and it would be possible to perform precision measurements for bothZ′and Higgs boson in future high-energye+e-colliders experiments.

scholarly journals Inclusive production of heavy quarkonia in pNRQCD

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Nora Brambilla ◽  
Hee Sok Chung ◽  
Antonio Vairo
Keyword(s):  
Cross Sections ◽  
Production Cross ◽  
Distance Matrix ◽  
Effective Field ◽  
Heavy Quarkonia ◽  
Inclusive Production ◽  
Theory Approach ◽  
Matrix Elements ◽  
Long Distance ◽  
Nonrelativistic Qcd

Abstract We develop a formalism for computing inclusive production cross sections of heavy quarkonia based on the nonrelativistic QCD and the potential nonrelativistic QCD effective field theories. Our formalism applies to strongly coupled quarkonia, which include excited charmonium and bottomonium states. Analogously to heavy quarkonium decay processes, we express nonrelativistic QCD long-distance matrix elements in terms of quarkonium wavefunctions at the origin and universal gluonic correlators. Our expressions for the long-distance matrix elements are valid up to corrections of order $$ 1/{N}_c^2 $$ 1 / N c 2 . These expressions enhance the predictive power of the nonrelativistic effective field theory approach to inclusive production processes by reducing the number of nonperturbative unknowns, and make possible first-principle determinations of long-distance matrix elements once the gluonic correlators are known. Based on this formalism, we compute the production cross sections of P-wave charmonia and bottomonia at the LHC, and find good agreement with measurements.

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