P. Artoisenet
I study the direct hadroproduction of Jψassociated with a charm-quark pair at leading order in alpha_S and v in NRQCD. This process provides an interesting signature that could be studied at the Tevatron. I consider both colour-singlet and colour-octet transitions. I compare our results to the fragmentation approximation and discuss the associated experimental signatures.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
We calculate the partonic cross sections for the hadroproduction of polarized chi_{cJ} mesons using the factorization formalism of nonrelativistic QCD. We also describe how the polarization is passed on to the J/psi mesons in the radiative feed-down chi_{cJ} -> J/psi + gamma and in the double-cascade decays of psi' mesons via chi_{cJ} intermediate states. These represent the missing ingredients needed to predict the polarization of prompt J/psi mesons at the Fermilab Tevatron.
The NRQCD factorization approach for quarkonium production at hadron colliders is reviewed. The prediction of J/psi and psi(2S) transverse polarization at large transverse momentum is confronted with recent experimental data, and potential shortcomings of the theoretical analysis are discussed.
Models with essential non-perturbative QCD dynamics and describing Tevatron data on high-$p_\perp$ charmonium are extrapolated to give predictions of prompt J/psi production at the LHC. Differences of up to an order of magnitude occurs. An important point is here the treatment of higher order perturbative QCD effects.
The double J/psi production in p\bar{p} collision is revisited. It is found that the J/ψpair production rate at leading order with p_T > 4 GeV in conventional scheme is larger than the rate derived from color-octet mechanism by a factor of five. As the double J/psi production is shown to be attainable with data yet collected at the Tevatron detectors, experimental study on it would be helpful to clarify the validity of the conventional color-singlet description for heavy quarkonium production.
Based on nonrelativistic QCD, we present the first complete next-to-leading order study on the polarization of prompt J/psi hadroproduction by including feeddown from chi_c(^3P_J^1,^3S_1^8) and psi(2s) which turn out to be a very important part. By using the color-octet long-distance matrix elements obtained from a combined fit of the differential cross section measurements at the Tevatron and LHC for J/psi, psi(2s) and chi_c with p_t>7GeV, the prompt J/psi polarization predictions are presented, and the results are in agree with the CDF Run-I data (except two points), but in conflict with the…
The polarization of prompt J/psi at the Tevatron is calculated within the nonrelativistic QCD (NRQCD) factorization framework. The contribution from radiative decays of P-wave charmonium states decreases, but does not eliminate, the transverse polarization at large transverse momentum. The prediction agrees with measurements from the CDF collaboration at intermediate values of p_T, but disagrees at the large values of p_T measured.
We study the effects of intrinsic transverse momentum smearing on J/psi production both at the Tevatron and at HERA. For the case of large-p_T J/psi production at the Tevatron, the effects due to k_T smearing are mild. On the other hand, inelastic J/psi photoproduction at HERA is very sensitive to the k_T smearing and, in fact, with a reasonable value of <k_T> it is possible to resolve the large-z discrepancy seen by comparing non-relativistic QCD (NRQCD) predictions with the HERA data. We conclude that, with the present kinematic cuts, photoproduction at HERA is not a good test of NRQCD.
Transverse polarization of ${}^3 S_1$ charmonium states, produced directly in $p\bar{p}$ collisions at asymptotically large transverse momentum p_t, has emerged as the most prominent test of color octet contributions and spin symmetry in quarkonium production. We present predictions for the polar angle distribution at moderate values of p_t \sim 4 - 20 GeV, covered by the Tevatron Run I data. We update the fits of NRQCD matrix elements and discuss their theoretical uncertainties. With our best fit values, no transverse polarization is expected at p_t \sim 5 GeV, but the angular distribution is…
Fragmentation production of J/psi and psi' at the Tevatron
本文计算了在Tevatron上大横动量时粲子和胶子碎裂对包含性$J/ψ$和$ψ'$产生的贡献。对于$ψ$的产生，我们包括直接裂解成$ψ$和裂解成$χ_c$，然后进行辐射衰变$χ_c \to ψ+ γ$。我们发现，碎片化的领先顺序机制，提示$ψ$生产在大$p_T$，和占主导地位的贡献来自碎片成$χ_c$。我们的结果与CDF和D 0实验中$ψ$生产的最新数据一致。在迅速产生$ψ'$的情况下，大$p_T$的主要机制是魅力碎裂成$ψ'$。我们发现我们的理论预测和最近的$ψ'$数据从Tevatron之间的严重分歧。
New data on high-pT spectra of J/psi measured by the CDF Collaboration at the Tevatron are analyzed in the framework of z-scaling. F-dependence of z-presentation of the data is used to construct the scaling function of J/psi. The energy independence of the scaling function is used to predict inclusive cross section of prompt J/psi production in bar pp collisions at high-pT. The concept of z-scaling is considered to reflect the general features of high-pT particle production in hadron-hadron and hadron-nucleus collisions. Violation of z-scaling is suggested to consider as a signature of new phy…
The next to leading order (NLO) QCD corrections to J/psi polarization of hadronproduction at Tevatron and LHC are calculated. The results show that the J/psi polarization is extremely changed from more transversal polarization at leading order (LO) into more longitudinal polarization at NLO. Although it gives more longitudinal polarization than the recent experimental result on the J/psi polarization at Tevatron. It sheds light on the solution to the large discrepancy of J/psi polarization between theoretical predication and experimental measurement, and suggests that the next important step i…
In the framework of NRQCD and parton model, we estimate in detail,the production cross section for polarized J/psi from B meson decays. In order to contrast with data, we also take into account additional J/psi production due to decay of excited charmonium states. We calculate the helicity parameter, alpha, and as an application, we study our results for the Tevatron. This is in contrast to the earlier studies which were performed for prompt J/psi production from p pbar collisions. Our estimates are, for J/psi from B decays, alpha_{J/psi} = -0.04 +- 0.06 and for B decays to psi', alpha_{psi'}=…
We report on our recent calculation of the inclusive direct photo- and hadroproduction of the J/psi meson at next-to-leading order within the factorization formalism of nonrelativistic QCD. We fit the color-octet (CO) long-distance matrix elements <O^(J/psi)(1S0[8])>, <O^(J/psi)(3S1[8])> and <O^(J/psi)(3P0[8])> to the transverse momentum (p_T) distributions measured by CDF at Fermilab Tevatron and by H1 at DESY HERA and show that they also successfully describe the p_T distributions from PHENIX at BNL RHIC and CMS at the CERN LHC as well as the photon-proton c.m. energy and (with worse agreeme…
J/psi+gamma Production at the Tevatron Energy
我们在Tevatron能量（$\sqrt{s} = 1.8$ ~TeV）下研究了过程$\bar p p \rightarrow J/ψ+ γ+X$.计算了微扰QCD对胶子融合和碎裂机制的贡献。对于整个范围的$p_T$，可以探测在Tevatron，融合的贡献被发现是占主导地位的。因此，QCD对这一过程的预测比$J/ψ$的纯强子产生有更好的精度。在Tevatron上对这一过程的实验研究将有助于澄清大$p_T$上夸克偶素产生的几个方面。
In this talk I show the results of a fit of the NRQCD matrix elements to the CDF data for direct $J/ψ$ production, by including the radiative corrections to the colour-singlet channel and the effect of the $k_T$-smearing. Furthermore I perform the NLO NRQCD analysis of $J/ψ$ production in fixed-target proton-nucleon collisions and I fit the colour-octet matrix elements to the available experimental data. The results are compared to the Tevatron ones.
The polarization of prompt J/psi at the Fermilab Tevatron is calculated within the nonrelativistic QCD factorization framework. The contribution from radiative decays of P-wave charmonium states decreases, but does not eliminate, the transverse polarization at large transverse momentum. The angular distribution parameter alpha for leptonic decays of the J/ψis predicted to increase from near 0 at p_T = 5 GeV to about 0.5 at p_T = 20 GeV. The prediction is consistent with measurements by the CDF Collaboration at intermediate values of p_T, but disagrees by about 3 standard deviations at the larg…
The recent measurements by CLEO Collaboration for the inclusive J/Psi and Psi(2S) production in Upsilon(1S) decay and our previous calculation are analyzed. The J/Psi momentum spectrum and the production ratio of Psi(2S) versus J/Psi favour Upsilon to J/Psi(Psi(2S)) + ccbar g as the dominant contribution. We point out that the differences between the experimental data and our previous results are mainly originated from the setting of the parameter charm quark mass. We further suggest the associate strange particle enhancement as a probe for the open charm particles in Upsilon to J/Psi (Psi(2S)…
We study prompt J/psi-meson hadroproduction invoking the hypothesis of gluon Reggeization in t-channel exchanges at high energy and the factorization formalism of nonrelativistic quantum chromodynamics at the leading order in the strong-coupling constant alpha_s and the relative velocity of quarks v. The transverse-momentum distribution of direct and prompt J/psi-meson production measured at the Fermilab Tevatron fitted to obtain the nonperturbative long-distance matrix elements, which are used to predict prompt J/psi production spectra at the CERN LHC. At the numerical calculation, we adopt t…
We compute leading-power fragmentation corrections to $J/ψ$ production at the Tevatron and the LHC. We find that, when these corrections are combined with perturbative corrections through next-to-leading order in the strong coupling constant $α_s$, we obtain a good fit to high-$p_T$ cross section data from the CDF and CMS Collaborations. The fitted long-distance matrix elements lead to predictions of near-zero $J/ψ$ polarization in the helicity frame at large $p_T$.
We review predictions, based on the nonrelativistic QCD factorization framework, for the polarizations of prompt J/psi's and Upsilon(nS)'s produced at the Fermilab Tevatron. We also discuss the effect of relativistic corrections on the theoretical prediction for the polarization of prompt J/psi's at the Tevatron.
We compare our theoretical results for charmed quark and J/Psi - photoproduction cross sections obtained in the semihard approach of QCD with H1 and ZEUS experimental data.
J/psi Production via Fragmentation at the Tevatron
考虑了在$p\bar p$碰撞中大横动量（$\pt > M_\jpsi$）下$\jpsi$的产生.考虑到碎裂到$\jpsi$和碎裂到$χ$状态然后辐射衰变到$\jpsi$的贡献。后者被认为是占主导地位的，比直接生产更大。整体的理论估计被证明是几乎与实验观察一致。
In this work, we present more detail of the calculation on the NLO QCD corrections to polarization of direct J/psi production via color singlet at Tevatron and LHC, as well as the results for Upsilon for the first time. Our results show that the J/psi polarization status drastically changes from transverse polarization dominant at LO into longitudinal polarization dominant in the whole range of the transverse momentum $p_t$ of J/psi when the NLO corrections are counted. For Upsilon production, the p_t distribution of the polarization status behaves almost the same as that for J/psi except that…
Color-Octet Fragmentation and the psi' Surplus at the Tevatron
在Tevatron中，在大横向动量下，瞬发$ψ'$的产生率比理论预期的大约30倍。作为这个难题的一个解决方案，我们建议占主导地位的$ψ'$生产机制是胶子分裂成一个$c \bar c$对在一个点状的色八重态S波状态，随后非微扰演化成一个$ψ'$加轻强子。相对于传统的颜色单重态贡献，通过$1/α_s^2$的短距离因子增强了来自该过程的对碎裂函数的贡献。这可以补偿$v^4$的抑制，其中$v$是$ψ'$中魅夸克的相对动量。如果这确实是$p_T$的主要产生机制，那么在Tevatron上观察到的瞬发$ψ'$应该几乎总是与轻强子喷流相关联。
We report on our recent evaluation of the s-channel cut contribution to J/psi hadroproduction. We show that it is likely significantly larger than the usual cut contribution of the colour-singlet model (CSM), which is known to underestimate the experimental measurements. Here the s-channel cut develops for configurations with off-shell quarks in the bound state. A correct treatment of its contribution requires the introduction of a four point function, partially constrained by gauge invariance and limiting behaviours at small and large momenta. When the unconstrained degrees of freedom are fix…
Using the statistical approach additional light partons have been introduced in the Intrinsic Charm model. Explicit expressions are obtained for charmed and light quark distributions. A comparison is made with standard IC model predictions. It is shown that such a modification of the IC model leads to better agreement with the $pN$ and $πN$ data on $\JP$ production at low energies and allows to avoid a contradiction to experimental data at high energy.
Production of open and hidden charm hadrons in heavy ion collisions is considered within the statistical coalescence model. Charmed quarks and antiquarks are assumed to be created at the initial stage of the reaction and their number is conserved during the evolution of the system. They are distributed among open and hidden charm hadrons at the hadronization stage in accordance with laws of statistical mechanics. The model is in excellent agreement with the experimental data on J/psi production in lead-lead collisions at CERN SPS and predicts strong enhancement of the open charm multiplicity o…
We present a complete evaluation for $\jpsi(\psip)$ prompt production at the Tevatron and LHC at next-to-leading order in nonrelativistic QCD, including color-singlet, color-octet, and higher charmonia feeddown contributions. The short-distance coefficients of $\pj$ at next-to-leading order are found to be larger than leading order by more than an order of magnitude but with a minus sign at high transverse momentum $p_T$. Two new linear combinations of color-octet matrix elements are obtained from the CDF data, and used to predict $\jpsi$ production at the LHC, which agrees with the CMS data. …
The direct production of $J/ψ(ψ')$ at large transverse momentum, $p_T \gg M_{J/ψ}$, at the Fermilab Tevatron is revisited. It is found that the sea-quark initiated processes dominate in the high-$p_T$ region within the framework of color-singlet model, which is not widely realized. We think this finding is enlightening for further investigation on the charmonium production mechanism.
We evaluate the form factors describing the semileptonic decays $\bar{B^0}\to J/ψ(η_c) D^+ \ell^- \bar ν_\ell$, within the framework of a QCD relativistic potential model. This decay is complementary to $\bar{B^0}\to J/ψ(η_c) D^+ π^-$ in a phase space region where a pion factors out.We estimate the branching ratio for these semileptonic and nonleptonic channels, finding $\mathcal{BR}(\bar{B^0} \to J/ψ(η_c) D^+ \ell ν_\ell) \simeq 10^{-13}$, $\mathcal{BR}(\bar{B^0} \to J/ψD^+ π^-) = 3.1 \times 10^{-8}$ and $\mathcal{BR}(\bar{B^0} \to η_c D^+ π^-) = 3.5 \times 10^{-8}$.
The remarkable discrepancy between theory and data on the p_t distribution of J/psi polarization in the process pp -> J/psi+X has been standing as a puzzle for a long time. Our early work indicates that if only considering the color-singlet state, NLO corrections may drastically change the distribution, but are not sufficient to accommodate the data. The color-octet intermediate state was suggested to make up the gap. Therefore a direct motivation is to evaluate if the NLO corrections to the J/psi production via a color-octet can indeed remedy the problem. Unfortunately, our results show that …
The production of the ${}^1P_1$ charmonium state, $h_c$, at large-$p_T$ at the Tevatron is considered. The colour-octet contributions to this state are found to be dominant and give a reasonably large rate for the production of $h_c$. This should make it feasible to look for this resonance in the $J/ψ+π$ decay channel. This production rate is a prediction of NRQCD, and the observation of the $h_c$ at the Tevatron can, therefore, be used as a test of the colour-octet predictions of NRQCD.
The interpretation of the J/psi suppression patterns observed in nuclear collisions, at CERN and RHIC, as a signature of the formation of a deconfined phase of QCD matter, requires knowing which fractions of the measured J/psi yields, in pp collisions, are due to decays of heavier charmonium states. From a detailed analysis of the available mid-rapidity charmonium hadro-production cross sections, or their ratios, we determine that the J/psi feed-down contributions from psi' and chi_c decays are, respectively, (8.1 +/- 0.3) % and (25 +/- 5) %. These proton-proton values are derived from global …
We briefly review recent results which we have obtained in the study of J/psi-pair production at the Tevatron and the LHC. We claim that the existing data set from CMS and D0 point at a significant double-parton-scattering contribution with an effective cross section smaller than that for jet-related observables. We have also derived simple relations involving feed-down fractions from excited states which can help in disentangling the single from the double scatterings.
The cross section for the photoproduction of large-p_T J/psi mesons at HERA is calculated at next-to-leading order, adopting a perturbative approach to describe the fragmentation of charm quarks and gluons into J/psi mesons. We treat the charm quark according to the massless factorization scheme, where it is assumed to be one of the active flavours inside the proton and the resolved photon. We present inclusive distributions in transverse momentum and rapidity, including the contributions due to direct and resolved photons. The importance of the colour-octet components of the J/psi wave functi…
We calculate the cross sections for the direct hadroproduction of J/psi and Upsilon associated with a heavy-quark pair of the same flavour at leading order in alpha_S and v in NRQCD. These processes provide an interesting signature that could be studied at the Tevatron and the LHC and also constitute a gauge-invariant subset of the NLO corrections to the inclusive hadroproduction of J/psi and Upsilon. We find that the fragmentation approximation commonly used to evaluate the contribution of these processes to the inclusive quarkonium production sizeably underestimates the exact calculation in …
We estimate the quantity |f_eta'^(c)| which is associated with the charm content of eta' meson from the experimentally known ratio R=B(psi ->eta' gamma )/B(psi ->eta_c gamma). It is shown that due to the off-shellness of the c\bar c component of eta', which has been overlooked so far, f_eta'^(c) is further suppressed. Assuming that psi ->eta' gamma decay is dominated by psi ->eta_c transition, we obtain |f_eta'^(c)| = 2.4 MeV which could imply that the (b -> c\bar cs) mechanism does not play a major role in the B -> K eta' decay mode.
We study the polarization observables of J/psi hadroproduction at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics. We complete the present knowledge of the relativistic corrections by also providing the contribution due to the intermediate ^3P_J^{[8]} color-octet states at this order, which turns out to be quite significant. Exploiting the color-octet long-distance matrix elements previously extracted through a global fit to experimental data of unpolarized J/psi production, we provide theoretical predictions in the helicity and Collins-Soper …
Nonrelativistic QCD provides a systematic approach for inclusive decays and productions of a quarkonium. By taking color-octet components into account, the approach can explain the $ψ'$-anomaly at Tevatron, where the measured production rate at large transverse momentum $p_\perp$ is in order of magnitude larger than the predicted with color-singlet components only. With the approach one can predict that the produced $J/ψ$ and $ψ'$ at large $p_\perp$ will be transversely polarized. But the prediction fails in confronting with experimental measurements and this generates a puzzle. We examine the…
We present an implementation of heavy quarkonium production within a perturbative QCD cascade based on the Colour Dipole Cascade model. We consider the processes most relevant in the context of the psi' surplus at the Tevatron; g -> psi' and c -> psi' in the colour-singlet model and g -> psi' through the colour-octet mechanism. Our implementation is, however, easily extendible to other quarkonia and other production mechanisms. Where comparison is possible we find good agreement with analytical calculations. We present some suggestions for measurements at the Tevatron that would be sensitive t…
Charmonia hadro- and photo-production are analyzed in the framework of the color-octet model taking into account higher-order effects induced by initial-state radiation of gluons. We argue that color-octet matrix elements obtained from Tevatron data might be reconciled with those extracted from HERA data on inelastic $J/ψ$ photoproduction. Finally we estimate cross sections for events with muons from prompt $J/ψ$'s as a background for the B physics programme at LHC experiments.
We report on a detailed investigation of exclusive J/psi production in proton--proton and proton-antiproton collisions. Predictions for Tevatron and LHC energies are included.
I review recent developments in theoretical understandings of J/psi productions in various processes at Tevatron, B decay and J/psi photoproduction including the color-octet mechanism.
We briefly review the existing psi(2S) data taken at RHIC, the Tevatron and the LHC. We systematically compare them with colour-singlet-model predictions as a function of the center-of-mass energy, of the quarkonium rapidity and of the quarkonium transverse momentum. The overall agreement is good except for large transverse momenta. This points at the existence of large NNLO corrections or points at colour-octet dominance.
In the framework of kt-factorization approach, the production and polarization of prompt psi(2S) mesons in pp collisions at the LHC energies is studied. Our consideration is based on the non-relativistic QCD formalism for bound states and off-shell amplitudes for hard partonic subprocesses. The transverse momentum dependent (unintegrated) gluon densities in a proton were derived from Ciafaloni-Catani-Fiorani-Marchesini evolution equation or, alternatively, were chosen in accordance with Kimber-Martin-Ryskin prescription. The non-perturbative color-octet matrix elements were first deduced from …
The cross sections for the charmonium production processes p pbar -> m Psi, where m is a light meson and Psi is a charmonium state, are of great interest for the planned p-pbar experiment PANDA. In this paper we estimate these cross sections using known results for the decays Psi -> m p pbar which are related to these reactions by crossing. In lieu of detailed experimental data on the decay Dalitz plots, we assume a constant amplitude as a first approximation; this implies a simple relation between the cross sections and decay widths. The single measured exclusive cross section of this type is…
Within a perturbative approach we investigate decays of charmonium states into baryon-antibaryon pairs. Using a recently proposed wave function for the nucleon and suitable generalizations of it to the hyperons and decouplet baryons, we obtain the decay widths for the baryon-antibaryon channels in reasonable agreement with data. An important difference to previous work is the use of the c-quark mass in the perturbative calculation instead of the charmonium mass. As a consequence of this feature our approach possesses, the J/Psi and the Psi' decay widths do not scale with a high power of the ra…
We determine the c-anti-c component of the photon wave function on the basis of (i) the data on the transitions e+ e- -> J/psi(3096), psi(3686), psi(4040), psi(4415), (ii) partial widths of the two-photon decays eta_{c0}(2979), chi_{c0}(3415), chi_{c2}(3556) -> gamma-gamma, and (iii) wave functions of the charmonium states obtained by solving the Bethe-Salpeter equation for the c-anti-c system. Using the obtained c-anti-c component of the photon wave function we calculate the gamma-gamma decay partial widths for radial excitation 2S state, eta_{c0}(3594) -> gamma-gamma, and 2P states chi_{c0}(…
Charmonium Production at the Tevatron
本文研究了强子碰撞中大- \pt粲偶素的产生。我们的工作框架中的分解模型的Bodwin Braaten和Lepage，从而包括颜色八重态的生产机制，并提取必要的非微扰参数的值与最近的数据从费米实验室1.8 TeV $p\bar p$强子对撞机的比较。我们将计算扩展到630 \gev，并将结果与UA 1协作组织发布的数据进行比较。全球协议是令人满意的，表明在高\pt \的粲生产机制的最大组件已被隔离。
Approximately taking into account the higher-order effects due to multiple-gluon initial-state radiation, we extract from the latest Tevatron data of prompt J/psi hadroproduction the leading colour-octet matrix elements within the nonrelativistic-QCD (NRQCD) factorization formalism. We find that the matrix elements which describe the formation of J/psi mesons from colour-octet c c-bar pairs in the angular-momentum states (2S+1)^L_J = 1^S_0 and 3^P_J, with J = 0, 1, 2, which are responsible for the excess of the predicted cross section of inelastic J/psi photoproduction over the existing HERA d…
Approximately taking into account the higher-order effects due to multiple-gluon initial-state radiation, we extract from the latest Tevatron data of prompt J/psi hadroproduction the leading colour-octet matrix elements within the nonrelativistic-QCD (NRQCD) factorization formalism proposed by Bodwin, Braaten, and Lepage. We find that the matrix elements which describe the formation of J/psi mesons from colour-octet cc-bar pairs in the angular-momentum states ^{2S+1}L_J = ^1S_0 and ^3P_J, with J = 0,1,2, which are responsible for the excess of the predicted cross section of inelastic J/psi pho…
Models with essential non-perturbative QCD dynamics for the production of charmonium are extrapolated to give predictions of prompt J/psi production at the LHC. Differences of up to an order of magnitude occurs, although the different models all describe the Tevatron data on high-pT charmonium. An important point is here the treatment of higher order perturbative QCD effects. We also discuss the large rate of prompt J/psi from these models as a background to CP violation studies.
Recent data from the CDF collaboration on the production of spin-triplet bottomonium states at the Tevatron p \bar p collider are analyzed within the NRQCD factorization formalism. The color-singlet matrix elements are determined from electromagnetic decays and from potential models. The color-octet matrix elements are determined by fitting the CDF data on the cross sections for Upsilon(1S), Upsilon(2S), and Upsilon(3S) at large p_T and the fractions of Upsilon(1S) coming from chi_b(1P) and chi_b(2P). We use the resulting matrix elements to predict the cross sections at the Tevatron for the sp…
We use the framework of a relativistic constituent quark model to study the semileptonic transitions of the Bc meson into CCbar charmonium states where CCbar = etaC (1S0), J/psi (3S1), chiC0 (3P0), chiC1 (3P1), hc (1P1), chiC2 (3P2), psi (3D2). We compute the q^2-dependence of all relevant form factors and give predictions for their semileptonic Bc decay modes including also their tau-modes. We derive a formula for the polar angle distribution of the charged lepton in the (l nu) c.m. frame and compute the partial helicity rates that multiply the angular factors in the decay distribution. For t…
We investigate the pattern of asymmetries in the colour-octet model for inclusive production of charmonium with polarised initial state hadrons and photons. We find that singly polarised asymmetries vanish. The double polarised asymmetry for J/psi involves a new combination of long-distance matrix element. We also investigate the asymmetries for eta_c, chi_c and Upsilon production. The asymmetries distinguish well between different models of charmonium production.
In e^+e^- annihilation at \sqrt{s}=10.6 GeV Belle Collaboration found, that J/psi mesons are predominantly produced in association with an extra \bar{c}c pair. The possible mechanisms of J/psi production are discussed and the probability of the associate production of \bar{c}c pair is estimated. The choice between these mechanisms can be done by measuring J/psi polarization. It is suggested, that in case of heavy ion collisions one may expect remarkable transverse polarization of produced J/psi, if quark-gluon plasma if formed. The measurement of asymmetry of e^+e^-(μ^+μ^-) angular distributio…
J/psi production via fragmentation at HERA
计算了胶子和粲夸克的碎裂对HERA大$p_T$ $J/ψ$产生的贡献。我们发现在大的$p_T$范围内，粲夸克碎裂的贡献超过了光子-胶子融合直接产生$J/ψ$的贡献，而胶子碎裂的贡献在整个$p_T$范围内都小到可以忽略不计.在HERA上对$J/ψ$的$p_T$分布的实验研究将提供对粲夸克碎裂函数的直接探测。
Consequences resulting from the D Dbar excess derived indirectly by the NA50 experiment in S+U and Pb+Pb collisions at sqrt(s)=19, 17 GeV, relevant for the identification of the QCD phase transition in these collisions, are discussed. The dependence of open and closed charm yields in Pb+Pb collisions on the number of participating nucleons (N) indicates non thermal charm production and J/Psi dissociation, stronger than the absorption seen in any other elementary hadron. The J/Psi in central Pb+Pb collisions could originate dominantly from c cbar pair coalescence out of a hadronizing quark and …
Hadrons produced in high-energy heavy-ion collisions can suppress the production of J/psi and other charmonium states by charmonium spontaneous dissociation as the hot hadronic environment alters the interaction between the charm quark and charm antiquark. Furthermore, hadrons can thermalize a charmonium to excite it to higher charmonium states which subsequently dissociate spontaneously. They can also collide with a charmonium to lead to its prompt dissociation into an open charm pair.
The production of J/Psi's in nuclei is re-examined and the critical role of Feynman x distributions in the study of photoproduction and hadronic production of both J/Psi's and Drell-Yan dimuons is expatiated. The need to consider both initial and final state interactions and the key effect of initial state interactions on the total J/Psi cross section are demonstrated. We use a Woods-Saxon Monte Carlo simulation to obtain distributions of the numbers of collisions prior and subsequent to the charmonium production. With those results we relate the mean number of nucleon-nucleon collisions, $<n>…
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。