We study inclusive $Λ_c^{\pm}$-baryon production in $pp$ collisions in the general-mass variable-flavor number scheme and compare with data from the LHCb, ALICE and CMS collaborations. We perform a new fit of the $c \to Λ_c^+$ fragmentation function combining $e^+e^-$ data from OPAL and Belle. The agreement with LHC data is slightly worse compared with a calculation using an older fragmentation function, and the tension between different determinations of $Λ_c^{\pm}$ production cross sections from the LHC experimental collaborations is not resolved. The ratio of data for $Λ_c^+$-baryon and $D^0$-meson production seems to violate the universality of $c$-charm quark to $c$-hadron fragmentation.
The Sivers Function is briefly reviewed and the Collins Fragmentation Function to produce a hadron from a polarized quark is defined. We estimate $π^{+},π^{-}$ +X production, where X represents particles which are not detected, via proton collisions with a polarized proton target using the Collins Fragmentation Function derived using the gluon distribution functions for polarized p-p collisions at E=$\sqrt{s}$=200 GeV.
We propose a method for measuring the hadron charge asymmetry in $\ee$ collisions which is based upon the fragmentation function formalism, and is largely independent of modelling of fragmentation effects. Furthermore, in this method, QCD radiative corrections can be accounted for in a systematic way.
We present a calculation of the charm and gluon fragmentation contributions to inclusive $J/ψ$ and $ψ'$ production at large transverse momentum at the Tevatron. For $ψ$ production, we include both fragmentation directly into $ψ$ and fragmentation into $χ_c$ followed by the radiative decay $χ_c \to ψ+ γ$. We find that fragmentation overwhelms the leading-order mechanisms for prompt $ψ$ production at large $p_T$, and that the dominant contributions come from fragmentation into $χ_c$. Our results are consistent with recent data on $ψ$ production from the CDF and D0 experiments. In the case of pro…
We present the preliminary results of a calculation of the fragmentation contribution to charmonium production at large transverse momentum in $p\bar{p}$ colliders. The fragmentation of gluons and charm quarks is the dominant direct production mechanism for sufficiently large $p_{\perp}$. We find that for both $J/ψ$ and $ψ'$ production fragmentation dominates over the conventional gluon-gluon fusion mechanism for $p_{\perp}$ greater than about 6 GeV.} Presented at the Workshop on Physics at Current Accelerator and the Supercollider, Argonne National Laboratory, June 1993.
We analyze the energy scale dependence of fragmentation functions from $e^+$-$e^-$ collisions using conventional momentum measures $x_p$ and $ξ_p$ and rapidity $y$. We find that replotting fragmentation functions on a normalized rapidity variable results in a compact form precisely represented by the beta distribution, its two parameters varying slowly and simply with parton energy scale $Q$. The resulting parameterization enables extrapolation of fragmentation functions to low $Q$ in order to describe fragment distributions at low transverse momentum $p_t$ in heavy ion collisions at RHIC.
An improved leading order fragmentation functions set of kaon is proposed based on the experimental data. We compare it with currently available sets, and use it to calculate high-$p_T$ $K/π$ ratios in relativistic proton-proton collisions. A prediction of $K/π$ ratios in relativistic nucleus-nucleus collisions ($d + Au$ and $Au + Au$) at RHIC $\sqrt{s} = 200$ GeV is given.
We compute the contributions to large-$p_T$ $J/ψ$ production at HERA coming from fragmentation of gluons and charm quarks. We find that the charm quark fragmentation contribution dominates over the direct production of $J/ψ$ via photon-gluon fusion at large-$p_T$, while the gluon fragmentation is negligibly small over the whole range of $p_T$. An experimental study of $p_T$ distributions of $J/ψ$ at HERA will provide a direct probe of the charm quark fragmentation functions.
We propose a modification of the mechanism of charmed quarks fragmentation into $D$ mesons in hadronic collisions. It is shown that the distinction in valence quark distributions in the initial $π^{\pm}$ and $K^{\pm}$ mesons leads to different inclusive spectra of $D$ and $D_s$ mesons produced in $π^{\pm}$ and $K^{\pm}$ beams.
The cross sections for the production of $B_s$ and $B_s^*$ mesons through the fragmentation process in $\bar{p}p$ collisions were calculated. The input parameters were determined from the measured $B_s$ and $B_s^*$ production rates in $e^+e^-$ annihilation. The transverse momentum distributions $dσ/dp_{T}$ are given for $\sqrt{s}=1.8$ TeV, the Fermilab Tevatron energy.
We review the physics of quarkonium production at high energy colliders, with a specific emphasis on production $via$ fragmentation. We discuss the fragmentation picture for the production of quarkonia at large-$p_T$ at the Tevatron and emphasise the importance of the colour-octet components of the quarkonium wave function which are included in the fragmentation functions. Applications of these theoretical ideas to other processes, both at the Tevatron and at other experiments like LEP, HERA and the LHC are important as they will provide stringent tests of these ideas.
We perform numerical comparison of the fragmentation mechanism of charmonium production ($g\,g\to c\,\bar{c}$ followed by $c\toψ\,c$) with the full leading order calculation ($g\,g\toψ\,c\,\bar{c}$ at $Ø (α_s^4)$). We conclude that the non-fragmentation contributions remain important up to $J/ψ$ transverse momenta about as large as 50 GeV, thus making questionable the applicability of the fragmentation approximation at smaller transverse momenta.
We study the impact of leading soft-collinear effects on threshold and joint-resummed calculations for the production of prompt photons via parton fragmentation, complementing a previous study for direct production. We assess these effects for both fixed-target and collider kinematics. We find them to be small, but noticeable and comparable to the direct case.
We discuss the polarised fragmentation functions of quarks and gluons in Perturbative Quantum Chromodynamics. The Altarelli-Parisi evolution equations governing these fragmentation functions are presented. We find that the first moment of the polarised gluon fragmentation function to order $α_s$ is as important as that of the quark and anti-quark fragmentation functions. The $Λ$ production in polarised $e^+ e^-$ annihilation where this can be realised is discussed. We propose the factorisation method to compute the gluonic contribution to $Λ$ production to order $α_s$. With appropriate operato…
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.
We use a recently completed O(alpha_s^2) fixed-order calculation of the heavy-flavour production cross section in e+e- collisions to compute the heavy-quark fragmentation function. We fit the result of our calculation, convoluted with a Peterson fragmentation function, to available data for charm production, and thus obtain a value for the parameter epsilon in the Peterson function. We discuss the relevance of mass effects and of subleading terms in our calculation.
Within the collinear twist-3 framework, we study the single-spin asymmetry (SSA) in collisions between unpolarized protons and transversely polarized protons with focus on the fragmentation term. The fragmentation mechanism must be analyzed in detail in order to unambiguously determine the impact of various contributions to SSAs in hadron production. Such a distinction may also settle the "sign mismatch" between the transverse SSA in proton-proton collisions and the Sivers effect in semi-inclusive deep inelastic scattering. We calculate terms involving quark-quark and quark-gluon-quark correla…
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.
The hydrodynamic (hydro) model applied to data from the relativistic heavy ion collider (RHIC) suggests that a dense QCD medium opaque to partons is formed in more-central Au-Au collisions. However, two-component spectrum analysis reveals a hard component, consistent with parton fragmentation described by pQCD, which can masquerade as "radial flow." Minimum-bias angular correlations reveal that most scattered partons survive as "minijets" even in central Au-Au collisions. Such alternative methods quantitatively describe spectrum and correlation structure via pQCD calculations. RHIC collisions …
Quarkonium production at a given large p_T is dominated by parton fragmentation: a parton which is produced with transverse momentum p_T/z fragments into a quarkonium state which carries a fraction z of the parton momentum. Since parton production cross sections fall steeply with p_T, high z fragmentation is favored. However, quantum number constraints may require the emission of gluons in the fragmentation process, and this softens the z dependence of the fragmentation function. We discuss the possibility that higher- order processes may enhance the large z part of fragmentation functions and…
Baryon production is studied within the framework of quantized fragmentation of QCD string. Baryons appear in the model in a fairly intuitive way, with help of causally connected string breakups. A simple helical approximation of QCD flux tube with parameters constrained by mass spectrum of light mesons is sufficient to reproduce masses of light baryons.
The Lambda baryons with a single heavy flavor which transfer the quark polarization, have been studied both theoretically and experimentally. The Xi's with two heavy constituents are well treated in quark-diquark model. In this work we study the production of triply heavy baryons in the perturbative QCD regime and calculate the fragmentation functions for Omega_ccc and Omega_bbb in the c and b quark fragmentation, respectively. We then obtain the total fragmentation probability and the average fragmentation parameter for each case.
We compute the contributions due to gluon and heavy-quark fragmentation to quarkonium production at large transverse momentum in $\bar p p$ and $p p$ collisions. For inclusive $J/ψ$ production, there is a large contribution from the $g \rightarrow χ_c$ fragmentation. At large $p_T$, this is comparable to the conventional charmonium model prediction via gluon fusion at the ISR and dominates over the latter at the Tevatron energy. This may help to explain, at least partly, the large $J/ψ$ production cross-section recently observed by the CDF experiment. However, the fragmentation contribution to…
The back-to-back $J/ψ$ and $π$ associated production at $e^+ e^-$ colliders is proposed to detect the gluon transverse momentum dependent(TMD) fragmentation functions. TMD factorization is assumed for this process. With spinless pion, unpolarized and linearly polarized gluon TMD fragmentation functions can be defined. It is found at parton level the hadronic tensor can be described by four structure functions. As a result, there are three independent angular distributions, of which a $\cos{2ϕ}$ azimuthal asymmetry is sensitive to the linearly polarized gluon fragmentation function.
The possibility to observe the medium-modified fragmentation of hard b-quarks tagged by a leading muon in ultrarelativistic heavy ion collisions is analyzed. We have found that reasonable statistics, ~20000 events per 1 month of LHC run with lead beams, can be expected for the realistic geometrical acceptance and kinematic cuts. The numerical estimates on the effect of the medium-induced softening b-jet fragmentation function are given.
An improved version of the ``pop-corn'' model for baryon production in quark and gluon jets is presented. With a reduced number of parameters the model reproduces well both production rates for different baryon species and baryon momentum distributions. Predictions are presented for a set of baryon-antibaryon correlations.
The production of $\jpsi$ at large transverse momenta ($\pt > M_\jpsi$) in $p\bar p$ collisions is considered by including the mechanism of fragmentation. Both contributions of fragmentation to $\jpsi$ and of fragmentation to $χ$ states followed by radiative decay to $\jpsi$ are taken into account. The latter is found to be dominant and larger than direct production. The overall theoretical estimate is shown to be nearly consistent with the experimental observation.
The dominant production mechanism for ${\bar b} c$ bound states in high energy processes is the production of a high energy ${\bar b}$ or $c$ quark, followed by its fragmentation into the ${\bar b} c$ state. We calculate the fragmentation functions for the production of the S-wave states $B_c$ and $B_c^*$ to leading order in the QCD coupling constant. The fragmentation probabilities for ${\bar b} \rightarrow B_c$ and ${\bar b} \rightarrow B_c^*$ are approximately $2.2 \times 10^{-4}$ and $3.1 \times 10^{-4}$, while those for $c \rightarrow B_c$ and $c \rightarrow B_c^*$ are smaller by almost t…
Parametrizations of fragmentation functions (FFs) from $e^+$-$e^-$ and p-p collisions are combined with a parton spectrum model in a pQCD folding integral to produce minimum-bias {\em fragment distributions}. A model of in-medium FF modification is included. Calculated fragment distributions are compared with {\em hard components} from p-p and Au-Au $p_t$ spectra. Data are well described by pQCD over a large kinematic region for a range of Au-Au centralities.
At hadron colliders the dominant production mechanism of $(\bar bc)$ mesons with large transverse momentum is due to parton fragmentation. We compute the rates and transverse momentum spectra for production of S-wave and P-wave $(\bar b c)$ mesons at the Tevatron via the direct fragmentation of the bottom antiquark as well as the Altarelli-Parisi induced gluon fragmentation. Since all the radially and orbitally excited $(\bar b c)$ mesons below the $BD$ flavor threshold will cascade into the pseudoscalar ground state $B_c$ through electromagnetic and/or hadronic transitions, they all contribut…
It has been known for a long time that hyperons produced in hadronic collisions are polarized perpendicular to the production plane of the reaction. This effect cannot be described by using twist-2 collinear parton correlators only. Here we compute the contribution of twist-3 fragmentation functions to the production of transversely polarized hyperons in unpolarized proton-proton collisions in the framework of collinear factorization. By taking into account the relations among the relevant twist-3 fragmentation functions which follow from the QCD equation of motion and the Lorentz invariance p…
By using a recently obtained set of Lambda fracture functions, we present predictions for Lambda production in the target fragmentation region of Semi-Inclusive Deep Inelastic Scattering in CLAS@12 GeV kinematics, supplemented with a conservative error estimates. We discuss a number of observables sensitive to the assumptions of the underlying theory and many of the assumptions of the proposed phenomenological model.
These lectures describe some of the latest data on particle production in high-energy collisions and compare them with theoretical calculations and models based on QCD. The main topics covered are: fragmentation functions and factorization, small-x fragmentation, hadronization models, differences between quark and gluon fragmentation, current and target fragmentation in deep inelastic scattering, and heavy quark fragmentation.
We discuss the possibility of the asymmetry in $D^-/D^+$ production, from $π^-$ beams, being a direct consequence of the properties of the light quark fragmentation function into heavy mesons. The main features of the asymmetry, as a function of $x_F$, are easily described. An integrated sum-rule for the $D^-, D^+$ difference, is presented. Predictions for the asymmetry, in $B$ meson production, are given.
Gluons cannot directly fragment into $B_c$ mesons until at order $α_s^3$. However, the Altarelli-Parisi evolution of the $\bar b$-quark fragmentation functions $D_{\bar b \to B_c}(z)$ and $D_{\bar b \to B_c^*}(z)$ from the heavy quark mass scales up to the collider energy scale $Q$ can induce the gluon fragmentation functions $D_{g \to B_c}(z)$ and $D_{g \to B_c^*}(z)$, respectively, through the gluon splitting $g\to \bar b$ at the order $α_s^3 \, {\rm log} (Q/m_{b,c})$. We will determine these induced gluon fragmentation functions. The $B_c$ meson productions due to the induced gluon fragment…
The rate for $ Z^{0}\to J/ ψ+ \ell^{+}\ell^{-} $ is suprisingly large with about one event for every million $Z^{0}$ decays. The reason for this is that there is a fragmentation contribution that is not suppressed by a factor of $M^{2}_ψ/M^{2}_{Z}$. In the fragmentation limit $ M_{Z}\to\infty$ with $E_ψ/M_{Z}$ fixed, the differential decay rate for $ Z^{0}\to J/ ψ+ \ell^{+}\ell^{-} $ factors into electromagnetic decay rates and universal fragmentation functions. The fragmentation functions for lepton fragmentation and photon fragmentation into $J/ψ$ are calculated to lowest order in $α$. The f…
Using a simple quark-diquark model, we extract a set of unpolarized and polarized fragmentation functions for the $Λ$ based on the available unpolarized $Λ$ production data in $e^+ e ^- $ annihilation. It is found that there is a strong SU(3) flavor symmetry breaking in the unpolarized $Λ$ fragmentation functions and that the polarized $u$ and $d$ quark contributions to the polarized $Λ$ fragmentation are positive in medium and large $z$ region. The predictions of $Λ$-polarization with the obtained quark fragmentation functions are compatible with the available data on the longitudinally polar…
The observed limiting fragmentation of charged particle distributions in heavy ion collisions is difficult to explain as it does not apply to the proton spectrum itself. On the other hand, string percolation provides a mechanism to regenerate fast particles, eventually compensating the rapidity shift (energy loss) of the nucleons. However a delicate energy-momentum compensation is required, and in our framework we see no reason for limiting fragmentation to be exact. A prediction, based on percolation arguments, is given for the charged particle density in the full rapidity interval at LHC ene…
We discuss baryon production in the nucleon fragmentation region in deep inelastic scattering. The dependence of the nucleon spectra on Bjorken-$x$ is evaluated within the parton model and in QCD, and ways to look for the break-down of the DGLAP approximation via baryon production are suggested. We argue also that the leading neutron production in these small $x$ processes is rather insensitive to the pion parton densities of the nucleon.
We report the recent progress in the studies of D-wave heavy quarkonia production from gluon fragmentation at the Tevatron and in Z^0 decays, and the D-wave charmonia production in B decays. We show that the color-octet contributions are of crucial importance to the production of D-wave quarkonia. Signals, as strong as that for J/ψand ψ^\prime, should be seen for the D-wave charmonium in the processes. These will provide a test of the color-octet production mechanism.
We study the twist-three fragmentation function contribution to the single transverse spin asymmetries in inclusive hadron production in pp collisions, pp->h+X. In particular, we evaluate the so-called derivative contribution which dominates the spin asymmetry in the forward direction of the polarized proton. With certain parametrizations for the twist-three fragmentation function, we estimate its contribution to the asymmetry of pi0 production at RHIC energy. We find that the contribution is sizable and might be responsible for the big difference between the asymmetries in eta and pi0 product…
During recent years, the study of exotic hadrons including tetraquarks and pentaquarks has attracted a lot of interests and more studies are in progress experimentally and theoretically. It is well-known that at sufficiently large transverse momentum the dominant production mechanism for standard heavy hadrons (mesons/baryons) is actually the fragmentation so that the same mechanism is also proposed for the production of heavy exotic hadrons. This work is the first attempt to study the direct fragmentation of a heavy quark into ground state heavy tetraquarks in leading order of perturbative QC…
We study the measurement of the quark fragmentation functions for spin-1/2 baryon production ($Λ$ and $\bar Λ$, in particular) in unpolarized $e^+e^-$ annihilation. The spin-dependent fragmentation functions $\hat g_1(z)$ and $\hat h_1(z)$ can be probed in the process as a result of quark-antiquark spin correlation and the weak decay of the baryons. The relevant cross section is expressed as a product of the two-jet cross-section, the fragmentation functions, and the differential width of the hyperon decay.
In this paper, we show that the distribution of the longitudinal momentum fraction of charged hadrons $dN/dz$ inside jets stemming from proton-proton collisions at $\sqrt{s}$ = 7 TeV center of mass energy can be described by a statistical jet-fragmentation model. This model combines microcanonical statistics and super-statistics induced by multiplicity fluctuations. The resulting scale dependence of the parameters of the model turns out to be similar to what was observed in electron-positron annihilations in Urmossy, Barnaföldi, and Biró.
We perform fits to the available charged and neutral kaon production data in $e^++e^-\to K+X$, $K=K^\pm and K^0_S$, and determine the non-singlet combination of kaon fragmentation functions $D_u^{K^\pm}-D_d^{K^\pm}$ in a model independent way and without any correlations to the other fragmentation functions. Only nuclear isospin invariance is assumed. Working with non-singlets allows us to include the data at very low momentum fractions, which have so far been excluded in global fits, and to perform a first NNLO fit to fragmentation functions. We find that the kaon non-singlet fragmentation fu…
We discuss the modification of a jet fragmentation function due to medium-induced partonic energy loss in context of leading particle observables in ultrarelativistic nucleus-nucleus interactions. We also analyze the relation between in-medium softening jet fragmentation function and suppression of the jet rates due to energy loss outside the jet cone. The predicted anti-correlation between two effects allows to probe a fraction of partonic energy loss carried out of the jet cone and truly lost to the jet.
The triply heavy baryons in the standard model formed in direct $c$ and $b$ quark fragmentation are the $Ω_{ccc}$, $Ω_{ccb}$, $Ω_{cbb}$ and $Ω_{bbb}$ baryons. We calculate their fragmentation functions in leading order of perturbative QCD. The universal fragmentation probabilities fall within the range of $10^{-5}-10^{-7}$.We also evaluate their cross section at the LHC ($\sqrt{s}=14$ TeV) using next-to-leading order matrix elements for heavy quark-antiquark pair production. We present the differential cross sections as functions of the transverse momentum as well as the total cross sections. …
We use a recent O(alpha_s^2) calculation of the differential cross section for the production of heavy quarks in e+e- annihilation to compute a few moments of the heavy quark single-inclusive production cross section. We verify that, contrary to some recent claims, the leading and next-to-leading logarithmic terms in this cross section are correctly given by the standard NLO fragmentation function formalism for heavy quark production.
In the framework of the kT-factorization approach we have calculated in the fragmentation model the pT-spectra of B(c) mesons at the energies of the Tevatron and the LHC Colliders and at the large pT domain. We compare the obtained results with the existing experimental data and with the predictions obtained in the collinear parton model.
We study the time-reversal odd quark fragmentation function and its consequences on the hard processes. T-odd quark fragmentation function may arise, although QCD is T-invariant, from the non-perturbative dynamics in the fragmentation process. Assuming the factorization, we extract the T-odd fragmentation function from the inclusive pion production in the transversely polarized proton-proton collision. We then estimate the single spin asymmetry $A_{OT}$ of the semi-inclusive deep inelastic scattering with unpolarized lepton and the transversely polarized proton. We also discuss the meson cloud…
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…
In charged current deep inelastic scattering charm is dominantly produced in scattering events on strange quarks, thereby allowing for an experimental determination of the nucleon's strange sea density. A measurement of the energy spectrum of final state charm fragments (D-mesons) determines the charm fragmentation function at spacelike scales considerably below typical e^+e^- c.m.s. energies. NLO corrections to the naive s -> c parton model production picture are important and well understood.
We calculate the fragmentation function for charm quark into J/psi at the QCD next-to-leading-order (NLO) and find that the produced J/psi is of larger momentum fraction than it is at the leading-order. Based on the fragmentation function and partonic processes calculated at the NLO, the transverse momentum distribution on J/psi hadroproduction associated with a charm c (or \bar{c}) jet are predicted. We find that the distribution is enhanced by a factor of 2.0--3.3 at the NLO as p_t increased from 10 GeV to 100 GeV and it is measurable at the LHC with charm tagger. The measurement at the LHC …
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 a model aimed at explaining jet quenching, large azimuthal asymmetry and baryon/meson ratio at large transverse momenta pt=2-10 GeV observed at RHIC. Its main point is that a QCD string can be cut by matter quarks and/or diquarks before its natural breaking. We model the early quark/diquark production via QCD sphalerons.
We compute the fragmentation functions for the production of a Higgs boson at $\mathcal{O}(y_t^2α_s)$. As part of this calculation, the relevant splitting functions are also derived at the same perturbative order. Our results can be used to compute differential cross sections with arbitrary top-quark and Higgs-boson masses from massless calculations. They can also be used to resum logarithms of the form $\ln(p_T/m)$ at large transverse momentum $p_T$ to next-to-leading-logarithmic accuracy by solving the DGLAP equations.
Hard components of $p_t$ spectra can be identified with minimum-bias parton fragmentation in nuclear collisions. Minimum-bias fragment distributions (FDs) can be calculated by folding a power-law parton energy spectrum with parametrized fragmentation functions (FFs) derived from $e^+$-$e^-$ and p-p collisions. Alterations to FFs due to parton "energy loss" or "medium modification" in Au-Au collisions are modeled by adjusting FF parametrizations consistent with rescaling QCD splitting functions. The parton spectrum is constrained by comparison with a p-p $p_t$ spectrum hard component. The refer…
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 $B_c$ …
The recently developed quantum mechanical string+${}^3P_0$ model of polarized quark fragmentation with pseudoscalar and vector meson production has been implemented in a stand alone Monte Carlo program. The simulation enables the detailed study of the quark spin dependent effects in the fragmentation process such as the transverse spin asymmetries. In particular, it allows to investigate the effects of the production and decay of vector mesons on the Collins and dihadron asymmetries of the observed hadrons, and to study the still unknown Collins effect for vector mesons. The main results of th…
It has recently been noticed that heavy quark ($Q$) and gluon ($g$) fragmentation to heavy quarkonium states ($Q\bar{Q}$) can be calculated in perturbative QCD. This technique allows for the inclusion of a subset of higher order corrections to quarkonium production which dominates at large transverse momentum. A comparison will be presented between the new calculation of quarkonium production to the existing data from the Tevatron. In addition some new results on predictions for double heavy quark baryons at various colliders will be presented.
