scholarly journals Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
M. I. Abdulhamid ◽  
M. A. Al-Mashad ◽  
A. Bermudez Martinez ◽  
G. Bonomelli ◽  
I. Bubanja ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Shower ◽  
Good Description ◽  
Leading Order ◽  
High Transverse Momentum ◽  
Azimuthal Correlation ◽  
Azimuthal Correlations ◽  
The Matrix ◽  
Good Agreement

AbstractThe azimuthal correlation, $$\Delta \phi _{12}$$ Δ ϕ 12 , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ s = 13  TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ Δ ϕ 12 is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi $$ Δ ϕ 12 → π , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ α s , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ Δ ϕ 12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution.

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 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 Drell-Yan angular lepton distributions at small x from TMD factorization.

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Ian Balitsky
Keyword(s):  
Transverse Momentum ◽  
Pair Production ◽  
Cross Section ◽  
Z Boson ◽  
Equation Of Motion ◽  
Leading Order ◽  
Small X ◽  
Mulders Function

Abstract The Drell-Yan process is studied in the framework of TMD factorization in the Sudakov region s » Q2 » $$ {q}_{\perp}^2 $$ q ⊥ 2 corresponding to recent LHC experiments with Q2 of order of mass of Z-boson and transverse momentum of DY pair ∼ few tens GeV. The DY hadronic tensors are expressed in terms of quark and quark-gluon TMDs with $$ \frac{1}{Q^2} $$ 1 Q 2 and $$ \frac{1}{N_c^2} $$ 1 N c 2 accuracy. It is demonstrated that in the leading order in Nc the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting hadronic tensors depend on two leading-twist TMDs: f1 responsible for total DY cross section, and Boer-Mulders function $$ {h}_1^{\perp } $$ h 1 ⊥ . The corresponding qualitative and semi-quantitative predictions seem to agree with LHC data on five angular coefficients A0− A4 of DY pair production. The remaining three coefficients A5− A7 are determined by quark-quark-gluon TMDs multiplied by extra $$ \frac{1}{N_c} $$ 1 N c so they appear to be relatively small in accordance with LHC results.

scholarly journals Power corrections in a transverse-momentum cut for vector-boson production at NNLO: the qg-initiated real-virtual contribution

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Carlo Oleari ◽  
Marco Rocco
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Cross Sections ◽  
Vector Boson ◽  
Analytic Form ◽  
Leading Order ◽  
Coupling Constant ◽  
Subtraction Method ◽  
Power Corrections ◽  
Interference Contribution

AbstractWe consider the production of a vector boson (Z, $$W^\pm $$ W ± or $$\gamma ^*$$ γ ∗ ) at next-to-next-to-leading order in the strong coupling constant $$\alpha _\mathrm{S}$$ α S . We impose a transverse-momentum cutoff, $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut , on the vector boson produced in the qg-initiated channel. We then compute the power corrections in the cutoff, up to the second power, of the real-virtual interference contribution to the cumulative cross section at order $$\alpha _\mathrm{S}^2$$ α S 2 . Other terms with the same kinematics, originating from the subtraction method applied to the double-real contribution, have been also considered. The knowledge of such power corrections is a required ingredient in order to reduce the dependence on the transverse-momentum cutoff of the QCD cross sections at next-to-next-to-leading order, when the $$q_{\mathrm{T}}$$ q T -subtraction method is applied. In addition, the study of the dependence of the cross section on $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut allows as well for an understanding of its behaviour in the small transverse-momentum limit, giving hints on the structure at all orders in $$\alpha _\mathrm{S}$$ α S and on the identification of universal patterns. Our result are presented in an analytic form, using the process-independent procedure described in a previous paper for the calculation of the all-order power corrections in $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut .

scholarly journals Multiplicative-accumulative matching of NLO calculations with parton showers

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Paolo Nason ◽  
Gavin P. Salam
Keyword(s):  
Phase Space ◽  
Matrix Element ◽  
Parton Shower ◽  
Leading Order ◽  
Positive Weight ◽  
New Approach ◽  
The Matrix ◽  
Core Features

Abstract We propose a new approach for combining next-to-leading order (NLO) and parton shower (PS) calculations so as to obtain three core features: (a) applicability to general showers, as with the MC@NLO and POWHEG methods; (b) positive-weight events, as with the KrkNLO and POWHEG methods; and (c) all showering attributed to the parton shower code, as with the MC@NLO and KrkNLO methods. This is achieved by using multiplicative matching in phase space regions where the shower overestimates the matrix element and accumulative (additive) matching in regions where the shower underestimates the matrix element, an approach that can be viewed as a combination of the MC@NLO and KrkNLO methods.

scholarly journals SIMULATION OF Z BOSON pT SPECTRUM AT TEVATRON BY LEADING-ORDER EVENT GENERATORS

2010 ◽  
Vol 25 (36) ◽  
pp. 3047-3059 ◽  
Author(s):  
SHIGERU ODAKA
Keyword(s):  
Transverse Momentum ◽  
Z Boson ◽  
Parton Shower ◽  
Event Generator ◽  
Boson Production ◽  
Proper Solution ◽  
Leading Order

We show that the transverse momentum (pT) spectrum of Z boson production measured at Fermilab Tevatron can be well reproduced by leading-order event generators if Z + 1 jet processes are included with a proper solution for the double-count problem and if the parton shower (PS) branch kinematics are defined appropriately. The choice of the PS evolution variable does not definitely determine the low-pT behavior. Our new event generator employing the limited leading-log (LLL) subtraction and a built-in leading-log PS reproduces the spectrum very well, not only in large pT regions but also at low pT down to pT = 0.

scholarly journals Azimuthal correlations of prompt D mesons with charged particles in pp and p–Pb collisions at $$\varvec{\sqrt{s_\mathrm{NN}}} = 5.02\ \hbox {TeV}$$

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
S. Acharya ◽  
◽  
D. Adamová ◽  
A. Adler ◽  
J. Adolfsson ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Correlation Function ◽  
Transverse Momentum ◽  
Correlation Functions ◽  
D Mesons ◽  
Charged Particles ◽  
Azimuthal Correlation ◽  
Side Peak ◽  
Azimuthal Correlations ◽  
Nuclear Effects

AbstractThe measurement of the azimuthal-correlation function of prompt D mesons with charged particles in pp collisions at $$\sqrt{s} =5.02\ \hbox {TeV}$$ s = 5.02 TeV and p–Pb collisions at $$\sqrt{s_{\mathrm{NN}}} = 5.02\ \hbox {TeV}$$ s NN = 5.02 TeV with the ALICE detector at the LHC is reported. The $$\mathrm{D}^{0}$$ D 0 , $$\mathrm{D}^{+} $$ D + , and $$\mathrm{D}^{*+} $$ D ∗ + mesons, together with their charge conjugates, were reconstructed at midrapidity in the transverse momentum interval $$3< p_\mathrm{T} < 24\ \hbox {GeV}/c$$ 3 < p T < 24 GeV / c and correlated with charged particles having $$p_\mathrm{T} > 0.3\ \hbox {GeV}/c$$ p T > 0.3 GeV / c and pseudorapidity $$|\eta | < 0.8$$ | η | < 0.8 . The properties of the correlation peaks appearing in the near- and away-side regions (for $$\Delta \varphi \approx 0$$ Δ φ ≈ 0 and $$\Delta \varphi \approx \pi $$ Δ φ ≈ π , respectively) were extracted via a fit to the azimuthal correlation functions. The shape of the correlation functions and the near- and away-side peak features are found to be consistent in pp and p–Pb collisions, showing no modifications due to nuclear effects within uncertainties. The results are compared with predictions from Monte Carlo simulations performed with the PYTHIA, POWHEG+PYTHIA, HERWIG, and EPOS 3 event generators.

QCD ANALYSIS OF DEEP INELASTIC LEPTON-NUCLEON SCATTERING DATA

1992 ◽  
Vol 07 (25) ◽  
pp. 2307-2315
Author(s):  
S. I. BILENKAYA ◽  
D. B. STAMENOV
Keyword(s):  
Cross Section ◽  
Scale Parameter ◽  
Structure Functions ◽  
Mass Scale ◽  
Scattering Data ◽  
Nucleon Structure ◽  
Leading Order ◽  
Parton Distributions ◽  
Qcd Analysis ◽  
Good Agreement

A combined next-to-leading order QCD analysis of BCDMS µ H 2 ( D 2) and CDHS [Formula: see text] scattering data is presented. The nucleon structure functions are given in terms of parton distributions. Unlike most of the papers on this subject, the cross-section scattering data (not the values for the nucleon structure functions extracted from these data by additional extrapolations and assumptions) are fitted. A very good agreement of the data with the predictions of QCD for the parton distributions is observed. The QCD mass scale parameter Λ is determined from these data both in a flavor nonsinglet approximation and with a complete flavor singlet and non-singlet treatment. These two fits to the data give consistent results for Λ.

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