Achieving the highest possible precision for theoretical predictions at the present and future high-energy lepton and hadron colliders requires a precise determination of fragmentation functions (FFs) of light and heavy charged hadrons from a global QCD analysis with great accuracy. We describe a simultaneous determination of unpolarized FFs of charged pions, charged kaons and protons/antiprotons from single-inclusive hadron production in electron-positron annihilation (SIA) data at next-to-leading order and next-to-next-to-leading order accuracy in perturbative QCD. A new set of FFs, called {\tt SGKS20}, is presented. We include data for identified light charged hadrons ($π^\pm, K^\pm$ and $p/\bar{p}$) as well as for unidentified light charged hadrons, $h^\pm$ and show that these data have a significant impact on both size and uncertainties of the fragmentation functions. We examine the inclusion of higher-order perturbative QCD corrections and finite-mass effects. We compare the new {\tt SGKS20} FFs with other recent FFs available in the literature and find in general reasonable agreement, but also important differences for some parton species. We show that theoretical predictions obtained from our new FFs are in very good agreement with the analyzed SIA data, especially at small values of $z$. The {\tt SGKS20} FF sets presented in this work are available via the {\tt LHAPDF} interface.
The fragmentation fractions of c and b quarks into the weakly decaying charmed hadrons D0, D+, D_s+ and Lambda_c+, and into the charmed vector meson D*+ have been derived from the LEP measurements and averaged. The c quark fragmentation fractions represent probabilities to hadronise as a given charmed hadron, while the b quark fragmentation fractions are defined as sums of probabilities to hadronise as a particular charmed hadron or its antiparticle.
Experimental data, theoretical ideas and models concerning jet fragmentation and the hadronization process are reviewed, concentrating on the following topics: factorization and small-x resummation of fragmentation functions, hadronization models, single-particle yields and spectra in Z decay, comparisons between quark and gluon jets, current and target fragmentation in deep inelastic scattering, heavy quark fragmentation, Bose-Einstein correlations and WW fragmentation.
We have measured the differential cross sections for the production of $π^{\pm}, K^{\pm}, K^0, K^{*0}, Φ, p$ and $Λ$ in hadronic $Z^0$ decays and in subsets of flavor-tagged $Z^0 \to$ light quark ($u \bar{u}$, $d \bar{d}$, or $s \bar{s}$), $Z^0 \to c \bar{c}$ and $Z^0 \to b \bar{b}$ events. Charged hadrons were identified with the SLD Cherenkov ring imaging detector. The vertex detector was employed to select flavor enriched samples and the polarized electron beam from SLC was used to tag quark and anti-quark jets. We observe a flavor dependence in the hadron fragmentation functions. We presen…
Determination of Fragmentation Functions from Charge Asymmetries in Hadron Production
State Key Laboratory of Dark Matter Physics, Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (MOE), School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院，粒子天体物理与宇宙学教育部重点实验室，暗物质物理全国重点实验室，粒子物理与宇宙学上海市重点实验室）
We present NNFF1.1h, a new determination of unidentified charged-hadron fragmentation functions (FFs) and their uncertainties. Experimental measurements of transverse-momentum distributions for charged-hadron production in proton-(anti)proton collisions at the Tevatron and at the LHC are used to constrain a set of FFs originally determined from electron-positron annihilation data. Our analysis is performed at next-to-leading order in perturbative quantum chromodynamics. We find that the hadron-collider data is consistent with the electron-positron data and that it significantly constrains the …
COMPASS final results on multiplicities of charged hadrons and of identified pions and kaons produced in the deep inelastic muon scattering off an isoscalar target are presented and compared to HERMES results. Measurements are done in bins of x, y and z in a wide kinematic range. The hadron and pion data show a good agreement with (N)LO QCD expectations. The kaon data are long awaited for since they are needed to extract kaon fragmentation functions, a crucial ingredient in solving the strange quark polarisation puzzle. COMPASS results for kaons differ from the expectations of the old NLO DSS …
The QCD coupling alpha_s is determined from a combined analysis of experimental e+e- and e-p jet data confronted to theoretical predictions of the energy evolution of the parton-to-hadron fragmentation functions (FFs) moments --multiplicity, peak, width, skewness-- at low fractional hadron momentum z. The impact of approximate next-to-leading order (NLO*) corrections plus next-to-next-to-leading log (NNLL) resummations, compared to previous LO+NLL calculations, is discussed. A global fit of the full set of existing data, amounting to 360 FF moments at collision energies sqrt(s)~1--200 GeV, res…
We discuss the inclusive high-pT charged-particle production in proton-proton collisions at the LHC. The experimental data are compared to the NLO perturbative QCD calculations employing various sets of parton-to-hadron fragmentation functions. Most of the theoretical predictions are found to disastrously overpredict the measured cross sections, even if the scale variations and PDF errors are accounted for. The problem appears to arise from the presently too hard gluon-to-hadron fragmentation functions.
We compute the contribution from the twist-3 fragmentation function for light hadron production in collisions between transversely and longitudinally polarized protons, i.e., $p^\uparrow \vec{p} \to h\,X$, which can cause a double-spin asymmetry (DSA) $A_{LT}$. This is a naïve T-even twist-3 observable that we analyze in collinear factorization using both Feynman gauge and lightcone gauge as well as give a general proof of color gauge invariance. So far only twist-3 effects in the transversely polarized proton have been studied for $A_{LT}$ in $p^\uparrow \vec{p} \to h\,X$. However, there are …
Hadron production in hard scattering reactions is described by the hadronization mechanism which combines quarks into final-state hadrons. Within the theoretical framework of leading-twist collinear QCD, the cross section for hadron production in semi-inclusive deep-inelastic scattering can be factorized into a hard scattering cross section describing the hard interaction at the quark level calculable in perturbative QED, and non-perturbative universal functions: parton distribution functions which reflect the quark structure of initial-state hadrons and collinear fragmentation functions which…
We present new sets of fragmentation functions for protons and inclusive charged hadrons obtained in combined NLO QCD analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering. These analyses complement previous results for pion and kaon fragmentation functions with charge and flavor discrimination. The Lagrange multiplier technique is used to assess the uncertainties in the extraction of the new sets of fragmentation functions.
We investigate the properties of interference fragmentation functions measurable from the distribution of two hadrons produced in the same jet in the current fragmentation region of a hard process. We discuss the azimuthal angular dependences in the leading order cross section of two-hadron inclusive lepton-nucleon scattering as an example how these interference fragmentation functions can be addressed separately.
We argue that the process $pp \to (\text{jet} γ)X$, for which a photon is observed inside a fully reconstructed jet and is treated as part of the jet, offers new probes of the so far little known fragmentation functions for photons. We present a next-to-leading-order QCD calculation of the cross section for this process in the limit that the jet is relatively narrow. We also investigate the background resulting from the two-photon decay of neutral pions. We present numerical results relevant for possible measurements at the LHC and at RHIC. These suggest that $pp \to (\text{jet} γ)X$ should pr…
Using the formalism of two-hadron fragmentation functions, we discuss single-spin asymmetries occurring in the production of two hadrons in the current region of deep inelastic scattering, with a particular emphasis on transversity measurements.
We introduce a broad class of fractal jet observables that recursively probe the collective properties of hadrons produced in jet fragmentation. To describe these collinear-unsafe observables, we generalize the formalism of fragmentation functions, which are important objects in QCD for calculating cross sections involving identified final-state hadrons. Fragmentation functions are fundamentally nonperturbative, but have a calculable renormalization group evolution. Unlike ordinary fragmentation functions, generalized fragmentation functions exhibit nonlinear evolution, since fractal observabl…
We reconsider the option of extracting the transversity distribution by using interference fragmentation functions into two leading hadrons inside the same current jet. To this end, we perform a new study of two-hadron fragmentation functions. We derive new positivity bounds on them. We expand the hadron pair system in relative partial waves, so that we can naturally incorporate in a unified formalism specific cases already studied in the literature, such as the fragmentation functions arising from the interference between the s- and p-wave production of two mesons, as well as the production o…
The description of the polarized quark hadronization process is one of the most challenging problems in the physics of strong interactions. The various single hadron and dihadron fragmentation functions, that quantify this process, are determined by analyzing the inclusive production of hadrons in electron-positron semi-inclusive annihilation process (SIA). These, in turn, are used to extract the transverse momentum dependent parton distribution functions from the experiments on semi-inclusive deep inelastic scattering process (SIDIS), elucidating the spin-orbit correlations in nucleon. Here w…
In the hadronic decays of Z, gluon emission leads to the appearance of the longitudinal component of the fragmentation function, F_L. Measurement of F_L and the transverse component, F_T, could thus provide an insight into the gluon fragmentation function. However, hadronization corrections at low x can be significant. Here we present a method of accounting for such corrections, using the JETSET event generator as illustration.
A next-to-leading order (NLO) analysis of hadron-jet momentum correlations in p-p collisions at the LHC is carried out. We show that the inclusive charged hadron momentum distributions inside jets is a very sensitive observable which allows one to disentangle among various fragmentation function sets presently available. Correlations with identified hadrons (kaons, protons) are investigated as well.
In this paper, we present a QCD analysis to extract the Fragmentation Functions (FFs) of unidentified light charged hadron entitled as SHK22.h from high-energy lepton-lepton annihilation and lepton-hadron scattering data sets. This analysis includes the data from all available single inclusive electron-positron annihilation (SIA) processes and semi-inclusive deep-inelastic scattering (SIDIS) measurements for the unidentified light charged hadron productions. The SIDIS data which has been measured by the COMPASS experiment could allow the flavor dependence of the FFs to be well constrained. We …
We study the inclusive production of two hadrons in deep inelastic processes, l N ---> l h_1 h_2 X, with h_1 in the current fragmentation region (CFR) and h_2 in the target fragmentation region (TFR). Assuming a factorized scheme, the recently introduced polarized and transverse momentum dependent fracture functions couple to the transverse momentum dependent fragmentation functions. This allows the full exploration of the fracture functions for transversely polarized quarks. Some particular cases are considered.
Fragmentation functions of pion, kaon, and nucleon are determined by global analyses of hadron-production data in $e^+e^-$ annihilation. It is particularly important that uncertainties of the fragmentation functions are estimated for the first time. We found that light-quark and gluon fragmentation functions have large uncertainties, so that one should be careful in using these functions for hadron-production processes in heavy-ion collisions and lepton scattering. The analysis is extended to possible exotic hadron search by fragmentation functions. We found that internal structure of $f_0 (98…
The fragmentation of a colored parton directly into a pair of colorless hadrons is a non-perturbative mechanism that offers important insights into the nucleon structure. Di-hadron fragmentation functions can be extracted from semi-inclusive electron-positron annihilation data. They also appear in observables describing the semi-inclusive production of two hadrons in deep-inelastic scattering of leptons off nucleons or in hadron-hadron collisions. When a target nucleon is transversely polarized, a specific chiral-odd di-hadron fragmentation function can be used as the analyzer of the net densi…
In this paper, we present ${\tt SGK18}$ FFs, a first global QCD analysis of parton-to-{\it unidentified} charged hadrons fragmentation functions (FFs) at next-to-next-to-leading order (NNLO) accuracy in perturbative QCD. This analysis is based on single-inclusive charged hadron production in electron-positron ($e^-e^+$) annihilation. The uncertainties in the extraction of ${\tt SGK18}$ FFs as well as the corresponding observables are estimated using the "Hessian" technique. We study the quality of the {\tt SGK18} FFs determined in this analysis by comparing with the recent results in literatur…
We shortly describe the leading twist formalism of spin and transverse-momentum dependent fracture functions recently developed and present results for the production of spinless hadrons in the target fragmentation region (TFR) of SIDIS. In this case not all fracture functions can be accessed and only a Sivers-like single spin azimuthal asymmetry shows up at LO cross-section. Then, we demonstrate that the measurement of spin dependent azimuthal asymmetries in double hadron production in polarized SIDIS -- with one spinless hadron produced in the current fragmentation region (CFR) and another i…
We present a novel global QCD analysis of charged $D^{*}$-meson fragmentation functions at next-to-leading order accuracy. This is achieved by making use of the available data for single-inclusive $D^{*}$-meson production in electron-positron annihilation, hadron-hadron collisions, and, for the first time, in-jet fragmentation in proton-proton scattering. It is shown how to include all relevant processes efficiently and without approximations within the Mellin moment technique, specifically for the in-jet fragmentation cross section. The presented technical framework is generic and can be stra…
We investigate the properties of interference fragmentation functions arising from the emission of two leading hadrons inside the same jet for semi-inclusive lepton-nucleon deep-inelastic scattering. Using an extended spectator model we give numerical estimates for the example of the fragmentation into a proton-pion pair with its invariant mass on the Roper resonance.
We shortly describe the leading twist formalism for spin and transverse-momentum dependent fracture functions recently developed and present results for the production of spinless hadrons in the target fragmentation region (TFR) of SIDIS. In this case not all fracture functions can be accessed and only a Sivers-like single spin azimuthal asymmetry shows up at LO cross-section. Then, we show that the process of double hadron production in polarized SIDIS -- with one spinless hadron produced in the current fragmentation region (CFR) and another in the TFR -- would provide access to all 16 leadin…
In this paper a new comprehensive analysis of parton-to-pion fragmentation functions (FFs) is performed for the first time by including all experimental data sets on single inclusive pion as well as unidentified light charged hadron production in electron-positron ($e^+e^-$) annihilation. We determine the pion FFs along with their uncertainties using the standard "Hessian" technique at next-to-leading order (NLO) and next-to-next-to leading order (NNLO) in perturabative QCD. It is shown that the determination of pion FFs using simultaneously the data sets from pion and unidentified light charg…
A novel method to extract the QCD coupling alpha_s from the energy evolution of the moments of the parton-to-hadron fragmentation functions at low fractional hadron momentum z, is presented. The evolution of the moments (multiplicity, peak, width, skewness) of the charged-hadron distribution in jets is computed at NMLLA+NLO* accuracy and compared to the experimental deep-inelastic e-p data. Values of the strong coupling constant at the Z pole are obtained, alpha_s(m_Z) = 0.119 +/- 0.010, in excellent numerical agreement with the current world average determined using other methods at the same …
In the literature it is assumed that the parton to hadron fragmentation function cannot be studied by using the lattice QCD method because of the sum over the (unobserved) outgoing hadronic states. However, in this paper we find that since the hadron formation from the partons can be studied by using the lattice QCD method, the parton to hadron fragmentation function can be studied by using the lattice QCD method by using the LSZ reduction formula for the partonic processes.
We apply collinear expansion to inclusive hadron production in $e^+e^-$ annihilation and derive a formalism suitable for systematic study of leading as well as higher twist contributions to fragmentation functions at the tree level. We make the calculations for hadrons with spin-0, spin-1/2 as well as spin-1 and obtain the results in terms of different components of fragmentation functions for the hadronic tensors, the differential cross section as well as hadron polarizations in different cases. The results show a number of interesting features such as the existence of transverse polarization…
It is proposed that fragmentation functions should be used to identify exotic hadrons. As an example, fragmentation functions of the scalar meson f_0(980) are investigated. It is pointed out that the second moments and functional forms of the u- and s-quark fragmentation functions can distinguish the tetraquark structure from $q\bar q$. By the global analysis of f_0 (980) production data in electron-positron annihilation, its fragmentation functions and their uncertainties are determined. It is found that the current available data are not sufficient to determine its internal structure, while …
Predictions for light charged hadron production data in the current fragmentation region of deeply inelastic scattering from the H1 and ZEUS experiments are calculated using perturbative Quantum Chromodynamics at next-to-leading order, and using fragmentation functions obtained by fitting to similar data from $e^+ e^-$ reactions. General good agreement is found when the magnitude $Q^2$ of the hard photon's virtuality is sufficiently large. The discrepancy at low $Q$ and small scaled momentum $x_p$ is reduced by incorporating mass effects of the detected hadron. By performing quark tagging, the…
I present a preliminary determination of the Fragmentation Functions (FFs) of unidentified charged hadrons at next-to-leading order in quantum chromodynamics. The analysis is based on hadron production cross section data in single-inclusive electron-positron annihilation. It extends a recent determination of the FFs of identified charged pions, charged kaons and protons/antiprotons performed by the NNPDF Collaboration. I illustrate the quality of the FFs determined in this analysis and show how they describe the charged hadron spectra measured in proton-(anti)proton collisions.
In this short review paper, we discuss some of the recent advances in the field of parton fragmentation processes into hadrons as well as their possible modifications in QCD media. Hadron production data in e+e-, deep inelastic scattering and hadronic collisions are presented, together with global analyses of fragmentation functions into light and heavy hadrons and developments on parton fragmentation in perturbative QCD at small momentum fraction. Motivated by the recent RHIC data indicating a significant suppression of large-pT hadron production in heavy-ion collisions, several recent attemp…
We present new sets of next-to-leading order fragmentation functions describing the production of charged pions, kaons and protons from the gluon and from each of the quarks, obtained by fitting to all relevant data sets from e+ e- annihilation. The individual light quark flavour fragmentation functions are obtained phenomenologically for the first time by including in the data the light quark tagging probabilities obtained by the OPAL Collaboration.
We propose the formulation of a dihadron fragmentation function in terms of parton matrix elements. Under the collinear factorization approximation and facilitated by the cut-vertex technique, the two hadron inclusive cross section at leading order (LO) in e+ e- annihilation is shown to factorize into a short distance parton cross section and the long distance dihadron fragmentation function. We also derive the DGLAP evolution equation of this function at leading log. The evolution equation for the non-singlet quark fragmentation function is solved numerically with a simple ansatz for the init…
Semi-inclusive deep inelastic scattering of polarized leptons off hadrons enables one to measure the antisymmetric part of the hadron tensor. For unpolarized hadrons this piece is odd under time reversal. In deep inelastic scattering it shows up as a $\langle \sin ϕ\rangle$ asymmetry for the produced hadrons. This asymmetry can be expressed as the product of a twist-three "hadron $\rightarrow$ quark" distribution function and a time reversal odd twist-two "quark $\rightarrow$ hadron" fragmentation function. This fragmentation function can only be measured for nonzero transverse momenta of the …
We investigate the role of heavy quarks in the production of light flavored hadrons and in the determination of the corresponding non perturbative hadronization probabilities. We define a general mass variable flavor number scheme for fragmentation functions that accounts for heavy quark mass effects, and perform a global QCD analysis to an up-to-date data set including very precise Belle and BaBar results. We show that the mass dependent picture provides a much more accurate and consistent description of data.
The role of hadronization mechanism in polarization phenomena in semi inclusive deep inelastic scattering (SIDIS) and a purity method for extraction of polarized distribution functions are discussed. According to the Monte Carlo (MC) event generator, on which this method is based, hadrons can be produced via quark (diquark) fragmentation or light cluster decays. In contrast, the purity method assumes that only quark fragmentation gives contribution to hadron production in the current fragmentation region. The ignorance of contributions from diquark fragmentation and cluster decays to asymmetry…
We present a model calculation of leading order interference fragmentation functions arising from the distribution of two hadrons produced in the same jet of a fragmenting quark in a hard process. Using a simple spectator model for the mechanism of the hadronization process, for the first time we give a complete calculation and numerical estimates for the example of a proton-pion pair production with its invariant mass on the Roper resonance.
Limiting fragmentation in proton-proton, deuteron-nucleus and nucleus-nucleus collisions is analyzed in the framework of the Balitsky-Kovchegov equation in high energy QCD. Good agreement with experimental data is obtained for a wide range of energies. Further detailed tests of limiting fragmentation at RHIC and the LHC will provide insight into the evolution equations for high energy QCD.
We present new sets of pion, kaon, proton and inclusive charged hadron fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either particles identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions.
The light top-squark $\sto$ may be the lightest squark and its lifetime may be `long enough' in a kind of SUSY models which have not been ruled out yet experimentally, so colorless `supersymmetric hadrons (superhadrons)' $(\sto \bar{q})$ ($q$ is a quark except $t$-quark) may be formed as long as the light top-squark $\sto$ can be produced. Fragmentation function of $\sto$ to heavy `supersymmetric hadrons (superhadrons)' $(\sto \bar{Q})$ ($\bar{Q}=\bar{c}$ or $\bar{b}$) and the hadronic production of the superhadrons are investigated quantitatively. The fragmentation function is calculated prec…
Semi-inclusive hadron-production processes are becoming important in high-energy hadron reactions. They are used for investigating properties of quark-hadron matters in heavy-ion collisions, for finding the origin of nucleon spin in polarized lepton-nucleon and nucleon-nucleon reactions, and possibly for finding exotic hadrons. In describing the hadron-production cross sections in high-energy reactions, fragmentation functions are essential quantities. A fragmentation function indicates the probability of producing a hadron from a parton in the leading order of the running coupling constant $α…
The bosonized QCD2+QED2 system for quarks with two flavors contains QCD2 and QED2 bound states, with an isoscalar photon at about 25 MeV and an isovector (I=1,I_3=0) photon at about 44 MeV. Consequently, when a quark and an antiquark at the two ends of a string pulls apart from each other at high energies, hadrons and soft photons will be produced simultaneously in the fragmentation of the string. The production of the QED2 soft photons in association with hadrons may explain the anomalous soft photon data in hadron-hadron collisions and e+e- annihilations at high energies.
We compute model-independently the production rates and transverse momentum spectra for the $B_c$ mesons in various spin-orbital states ($n\,^1S_0$, $n\,^3S_1$, $n\,^1P_1$, and $n\,^3P_J\,(J=0,1,2)$ ) at hadron colliders via the direct fragmentation of the bottom antiquark and via the Altarelli-Parisi-induced gluon fragmentation. Since all the radially and orbitally excited states below the $BD$ flavor threshold will decay, either electromagnetically, hadronically, or a combination of both, into the pseudoscalar ground state $1\,^1S_0$, they all contribute significantly to the inclusive $B_c$ …
It is demonstrated that the fragmentation functions at large momentum fraction play a key role in hard hadron production from relativistic proton-proton collisions. We find that this region of the fragmentation functions is not strongly constrained by the electron-positron data. This freedom can be used (together with the transverse momentum distribution of partons) to reproduce hard pion-to-proton ratio data in relativistic proton-proton collisions.
Using methods of effective field theory, a systematic analysis of the fragmentation functions D_{a/H}(x,m_Q) of a hadron H containing a heavy quark Q is performed (with a=Q,Q_bar,q,q_bar,g). By integrating out pair production of virtual and real heavy quarks, the fragmentation functions are matched onto a single nonperturbative function describing the fragmentation of the heavy quark Q into the hadron H in "partially quenched" QCD. All calculable, short-distance dependence on x is extracted in this step. For x->1, the remaining fragmentation function can be matched further onto a universal fun…
Theoretical understanding of the observed jet quenching measurements at RHIC and LHC is challenging in QCD because it requires understanding of parton to hadron fragmentation function in non-equilibrium QCD. In this paper, by using closed-time path integral formalism, we derive the gauge invariant definition of the gluon to hadron fragmentation function in non-equilibrium QCD which is consistent with factorization theorem in non-equilibrium QCD from first principles.
Nuclear multifragmentation process can be viewed as a recombination of nucleons into clusters of various sizes. In a combinatorial analysis, various moments of cluster size distribution appear to be quite simple in terms of canonical partition functions. This simple model can also describe a branching phenomena and a clusterization phenomena. The possibility of applying this fragmentation model in describing a hadronization of quark-gluon system and a strangeness production is discussed.
We present the complete structure of the azimuthal dependences and polarization observables for two-hadron production in $e^+e^-$ annihilation processes within a transverse momentum dependent (TMD) approach adopting the helicity formalism. The leading-twist TMD fragmentation functions (TMD-FFs) for spin-1/2 hadrons are fully accounted for. The role of the polarizing FF, together with its extraction from Belle data for the transverse polarization of $Λ$'s, are discussed as well. Finally, predictions for SIDIS processes at EIC are presented.
We present a reliable estimate on the production rate of $B_c$ mesons in $1S$ and $2S$ states in the large transverse momentum region at hadronic colliders using heavy quark fragmentation functions derived within the framework of perturbative QCD. We also present the transverse momentum distribution for the $B_c$ mesons. The production rate is large enough for the $B_c$ mesons to be identified at the Tevatron. At the SSC/LHC the rate is so large that their properties can be studied in details.
We propose the characterization of fragmentation functions by the energy fraction x, a hadron takes away from the energy of the jet measured in the frame co-moving with the jet. Besides, we propose the usage of the jet mass as the fragmentation scale Q. We show that these two Lorentz-invariant variables emerge naturally in a microcanonical ensemble with conserved fourmomentum. Then, we construct a statistical hadronisation model, in which, two features of the hadronic final states in various high-energy reactions (power law spectra and negative-binomial multiplicity distributions) can be conne…
We discuss studies on determination of fragmentation functions and an application to exotic-hadron search by using characteristic differences between favored and disfavored functions. The optimum fragmentation functions are determined for pion, kaon, and proton in the leading order (LO) and next-to-leading order (NLO) of the running coupling constant alpha_s by global analyses of hadron-production data in electron-positron annihilation. Various parametrization results are much different in disfavored-quark and gluon fragmentation functions; however, we show that they are within uncertainties o…
