scholarly journals Fragmentation of ω and ϕ mesons in e+e− and pp collisions at NLO

2017 ◽  
Vol 32 (33) ◽  
pp. 1750199
Author(s):  
H. Saveetha ◽  
D. Indumathi
Keyword(s):  
Transverse Momentum ◽  
Differential Cross Section ◽  
Cross Section ◽  
Leading Order ◽  
Text Data ◽  
Quark Fragmentation ◽  
Fragmentation Functions ◽  
Error Bars ◽  
First Time ◽  
Gluon Fragmentation

A combined analysis of both [Formula: see text] (LEP, SLD) and [Formula: see text] (RHIC-PHENIX and LHC-ALICE) hadroproduction processes are done for the first time for the vector meson nonet at the next-to-leading order (NLO) using a model with broken SU(3) symmetry. The transverse momentum ([Formula: see text]) and rapidity ([Formula: see text]) dependence of the differential cross-section for [Formula: see text] and [Formula: see text] mesons of the [Formula: see text] data are also discussed. The input universal quark (valence and singlet) fragmentation functions at a starting scale of [Formula: see text], after evolution, have values that are consistent with the earlier analysis for [Formula: see text] at NLO. However, the universal gluon fragmentation function is now well determined from this study with significantly smaller error bars, as the [Formula: see text] hadroproduction cross-section is particularly sensitive to the gluon fragmentation since it occurs at the same order as the quark fragmentation, in contrast to the [Formula: see text] hadroproduction process. Additional parameters involved in describing the strangeness and sea suppression and octet–singlet mixing are found to be close to the earlier analysis; in addition, a new relation between the gluon and sea suppression in [Formula: see text] and [Formula: see text] hadroproduction has been observed.

scholarly journals Vector meson fragmentation using a model with broken SU(3) at the next-to-leading order

2014 ◽  
Vol 29 (07) ◽  
pp. 1450049 ◽  
Author(s):  
H. Saveetha ◽  
D. Indumathi ◽  
Subhadip Mitra
Keyword(s):  
Vector Meson ◽  
Cross Section ◽  
Evolution Equations ◽  
Light Quark ◽  
Energy Scale ◽  
Dglap Evolution ◽  
Leading Order ◽  
Quark Fragmentation ◽  
Fragmentation Functions ◽  
The Cross

A detailed study of fragmentation of vector mesons at the next-to-leading order (NLO) in QCD is given for e+e- scattering. A model with broken SU(3) symmetry using three input fragmentation functions α(x, Q2), β(x, Q2) and γ(x, Q2) and a strangeness suppression parameter λ describes all the light quark fragmentation functions for the entire vector meson octet. At a starting low energy scale of [Formula: see text] for three light quarks (u, d, s) along with initial parametrization, the fragmentation functions are evolved through DGLAP evolution equations at NLO and the cross-section is calculated. The heavy quarks contribution are added in appropriate thresholds during evolution. The results obtained are fitted at the momentum scale of [Formula: see text] for LEP and SLD data. Good-quality fits are obtained for ρ, K*, ω and ϕ mesons, implying the consistency and efficiency of this model. Strangeness suppression in this model is understood both in terms of ratios of quark fragmentation functions alone as well as in terms of observables; the latter yield a suppression through the K*/ρ multiplicity ratio of about 0.23 while the x dependence of this suppression is also parametrized through the cross-section ratios.

scholarly journals Measurements of triple-differential cross sections for inclusive isolated-photon+jet events in $$\mathrm{p}\mathrm{p}$$ collisions at $$\sqrt{s} = 8\,\text {TeV} $$

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Phase Space ◽  
Transverse Momentum ◽  
Differential Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Leading Order ◽  
Perturbative Quantum Chromodynamics ◽  
Triple Differential Cross Section ◽  
Perturbative Quantum

AbstractMeasurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in $$\mathrm{p}\mathrm{p}$$pp collisions at $$\sqrt{s} = 8$$s=8 TeV as a function of photon transverse momentum ($$p_{\mathrm {T}} ^{{\upgamma {}{}}}$$pTγ), photon pseudorapidity ($$\eta ^{{\upgamma {}{}}}$$ηγ), and jet pseudorapidity ($$\eta ^{\text {jet}}$$ηjet). The data correspond to an integrated luminosity of $$19.7{\,\text {fb}^{-1}} $$19.7fb-1 that probe a broad range of the available phase space, for $$|\eta ^{{\upgamma {}{}}} |<1.44$$|ηγ|<1.44 and $$1.57<|\eta ^{{\upgamma {}{}}} |<2.50$$1.57<|ηγ|<2.50, $$|\eta ^{\text {jet}} |<2.5$$|ηjet|<2.5, $$40< p_{\mathrm {T}} ^{{\upgamma {}{}}}<1000$$40<pTγ<1000$$\,\text {GeV}$$GeV, and jet transverse momentum, $$p_{\mathrm {T}} ^{\text {jet}}$$pTjet, > 25$$\,\text {GeV}$$GeV. The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.

scholarly journals Factorization of e+e− → H X cross section, differential in zh, PT and thrust, in the 2-jet limit

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
M. Boglione ◽  
A. Simonelli
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Belle Collaboration ◽  
Hadron Production ◽  
Leading Order ◽  
Transverse Momentum Dependent ◽  
Factorization Scheme ◽  
Phenomenological Studies ◽  
Cross Section Differential ◽  
Perturbative Part

Abstract Factorizing the cross section for single hadron production in e+e− annihilations is a highly non trivial task when the transverse momentum of the outgoing hadron with respect to the thrust axis is taken into account. We work in a scheme that allows to factorize the e+e−→ H X cross section as a convolution of a calculable hard coefficient and a Transverse Momentum Dependent (TMD) fragmentation function. The result, differential in zh, PT and thrust, will be given to all orders in perturbation theory and explicitly computed to Next to Leading Order (NLO) and Next to Leading Log (NLL) accuracy. The predictions obtained from our computation, applying the simplest and most natural ansatz to model the non-perturbative part of the TMD, are in exceptional agreement with the experimental measurements of the BELLE Collaboration. The factorization scheme we propose relates the TMD parton densities defined in 1-hadron and 2-hadron processes, restoring the possi- bility to perform global phenomenological studies of TMD physics including experimental data from semi-inclusive deep inelastic scattering, Drell-Yan processes, e+e−→ H1H2X and e+e−→ H X annihilations.

BESSEL-WEIGHTED ASYMMETRIES AND TRANSVERSE SPIN EFFECTS

2012 ◽  
Vol 20 ◽  
pp. 168-176
Author(s):  
LEONARD GAMBERG
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Distribution ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Transverse Spin ◽  
High Transverse Momentum ◽  
Transverse Momentum Dependent ◽  
Fragmentation Functions ◽  
The Cross

We consider the cross section for semi-inclusive deep inelastic scattering in Fourier space, conjugate to the outgoing hadron's transverse momentum, where convolutions of transverse momentum dependent parton distribution functions and fragmentation functions become simple products. Individual asymmetric terms in the cross section can be projected out by means of a generalized set of weights involving Bessel functions. Advantages of employing these Bessel weights are that they suppress (divergent) contributions from high transverse momentum and that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions and to quantities accessible in lattice QCD. Bessel-weighted asymmetries are thus model independent observables that augment the description and our understanding of correlations of spin and momentum in nucleon structure.

scholarly journals CHARMONIUM PRODUCTION AT THE LHC

1996 ◽  
Vol 11 (19) ◽  
pp. 1555-1562 ◽  
Author(s):  
K. SRIDHAR
Keyword(s):  
Cross Section ◽  
Event Rate ◽  
Charm Quark ◽  
Large Transverse Momentum ◽  
Fragmentation Mechanism ◽  
Charmonium Production ◽  
Quark Fragmentation ◽  
Gluon Production ◽  
Gluon Fragmentation ◽  
Important Test

The analyses of large transverse momentum charmonium production at the Tevatron have shown that fragmentation of gluons is an important production mechanism. We study large-pT charmonium production in pp collisions at the LHC, and find that due to the copious gluon production at this energy, the gluon fragmentation contribution completely overwhelms the fusion contribution and the charm quark fragmentation contribution. Our analysis shows that for J/ψ production at the LHC, there is a significant event rate even for pT ~ 100 GeV. The measurement of the cross-section at such large values of pT will provide a very important test of the fragmentation mechanism.

scholarly journals General helicity formalism for two-hadron production in e+e− annihilation within a TMD approach

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Umberto D’Alesio ◽  
Francesco Murgia ◽  
Marco Zaccheddu
Keyword(s):  
Transverse Momentum ◽  
Hadron Production ◽  
Probabilistic Interpretation ◽  
Leading Order ◽  
Transverse Momentum Dependent ◽  
Factorization Scheme ◽  
Helicity Formalism ◽  
Double Polarization ◽  
Fragmentation Functions ◽  
Polarization Observables

Abstract We present the complete leading-order results for the azimuthal dependences and polarization observables in e+e−→ h1h2 + X processes, where the two hadrons are produced almost back-to-back, within a transverse momentum dependent (TMD) factorization scheme. We consider spinless (or unpolarized) and spin-1/2 hadron production and give the full set of the corresponding quark and gluon TMD fragmentation functions (TMD-FFs). By adopting the helicity formalism, which allows for a more direct probabilistic interpretation, single- and double-polarization cases are discussed in detail. Simplified expressions, useful for phenomenological analyses, are obtained by assuming a factorized Gaussian-like dependence on intrinsic transverse momenta for the TMD-FFs.

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 COMPASS Measurement of Pion and Kaon Multiplicities and Extraction of Quark Fragmentation Functions into Pions

2016 ◽  
Vol 40 ◽  
pp. 1660027
Author(s):  
Fabienne Kunne
Keyword(s):  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Leading Order ◽  
Data Set ◽  
Quark Fragmentation ◽  
Z Domain ◽  
Fragmentation Functions

We present preliminary COMPASS results on pion and kaon multiplicities produced in semi inclusive deep inelastic scattering of 160[Formula: see text]GeV muons off an isoscalar ([Formula: see text]LiD) target. The results constitute an impressive data set of more than 400 points in p and 400 in K, covering a large x,Q[Formula: see text] and z domain in a fine binning, which will be used in future QCD fits at next to leading order to extract quark fragmentation functions. We show results of a first leading order fit performed to extract the favored and unfavored quark fragmentation functions into pions D[Formula: see text] and D[Formula: see text].

Production cross-section of heavy flavored hadrons in pp collision at s = 7 TeV

2019 ◽  
Vol 34 (19) ◽  
pp. 1950150 ◽  
Author(s):  
Muhammad Ajaz ◽  
Irfan Khan ◽  
M. K. Suleymanov
Keyword(s):  
Experimental Data ◽  
Transverse Momentum ◽  
Differential Cross Section ◽  
Cross Section ◽  
Momentum Distribution ◽  
Cross Sections ◽  
Production Cross ◽  
Center Of Mass ◽  
Transverse Momentum Distribution ◽  
Mass Frame

The transverse momentum distribution of the differential production cross-sections of heavy flavored charm hadrons [Formula: see text], [Formula: see text] in pp collisions at 7 TeV are simulated. Predictions of DPMJETIII.17-1, HIJING1.383 and Sibyll2.3c are compared to the differential cross-section measurements of the LHCb experimental data presented in the region of [Formula: see text] and [Formula: see text], where the pp center of mass frame is used to measure the transverse momentum and rapidity. The models reproduce only some regions of [Formula: see text] and/or bins of [Formula: see text] but none of them predict completely all the [Formula: see text] bins over the entire [Formula: see text] range.

scholarly journals KSΛ PHOTOPRODUCTION ON THE NEUTRON WITHIN THE RESONANCE REGION

2014 ◽  
Vol 26 ◽  
pp. 1460100
Author(s):  
◽  
CHARLES TAYLOR ◽  
PHILIP COLE
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Photon Energy ◽  
Differential Cross ◽  
Center Of Mass ◽  
Resonance Region ◽  
Reaction Threshold ◽  
Circularly Polarized ◽  
Large Acceptance ◽  
First Time

We report some preliminary differential cross section results for the γ d → KSΛ(p) reaction using a circularly-polarized photon beam and an unpolarized LD2 target. The data was collected at the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. For this study the photon energy ranged from 1.3 to 2.53 GeV, which covers from the reaction threshold through the nucleon resonance regimes. The acceptance- and flux-corrected yields show peaks at the center-of mass energies W = 1.7 and W = 1.9 GeV. These first-time results will aid in unraveling the spectrum of non-strange excited baryons.

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