The like-sign dimuon charge asymmetry at the Tevatron: corrections from B meson fragmentation
Alexander Mitov
备注：
7 pages, 2 figures. v2:journal version. Added Eq.22 and table 2 (were implicit in figs.1,2 in v1) and 3 ref's. Note Added about new measurements from LHCb and CDF that confirm our theoretical arguments to use the values of f_s and f_d from Z pole data
The existing predictions for the like-sign dimuon charge asymmetry at the Tevatron are expressed in terms of parameters related to B mesons' mixing and inclusive production fractions. We show that in the realistic case when phase-space cuts are applied, the asymmetry depends also on the details of the production mechanism for the B mesons. In particular, it is sensitive to the difference in the fragmentation functions of B^0_d and B^0_s mesons. We estimate these fragmentation effects and find that they shift the theory prediction for this observable by approximately 10%. We also point out the approximately 20% sensitivity of the asymmetry depending on which set of values for the B meson production fractions is used: as measured at the Z pole or at the Tevatron. The impact of these effects on the extraction of A^s_{SL} from the DØmeasurement is presented.
We show that the recently measured 3.2 $σ$ deviations of the charge asymmetry of like-sign dimuon events from the standard model prediction by the D0 collaboration at Tevatron can be explained by introducing the anomalous right-handed top quark couplings. Combined analysis with the $\bs$ and $\bd$ mixings and $B \to X_s γ$ decays has been performed. We discuss how to discriminate the effects on the dimuon charge asymmetry of the anomalous $\tsW$ and $\tbW$ couplings.
The dimuon plus dijet signal is analyzed in the top squark pair production at Tevatron Run-II experiment and the total event rate is compared with the existing dimuon data. This comparison rules out top squark mass upto 188(104) GeV for the branching fraction 100%(50%) of top squark decay into the muon plus quark via lepton number violating coupling. Interpretation of this limit in the framework of R-parity violating(RPV) SUSY model puts limit on relevant RPV coupling for a given top squark mass and other supersymmetric model parameters. If $\MST \lsim 180$ GeV we found that the RPV couplings …
The DØ collaboration has measured the like-sign dimuon charge asymmetry in $p \bar{p}$ collisions at the Fermilab Tevatron collider. The result is significantly different from the standard model expectation of CP violation in mixing. In this paper we consider the possible causes of this asymmetry and identify one standard model source not considered before. It decreases the discrepancy of the like-sign dimuon charge asymmetry with the standard model prediction, although does not eliminate it completely.
The recently measured charge asymmetry of like-sign dimuon events by the D0 collaboration at Tevatron shows the 3.9 σ deviation from the standard model prediction. In order to solve this mismatch, we investigate the right-handed current contributions to $B_s-\bar{B}_s$ and $B_d-\bar{B}_d$ mixings which are the major source of the like-sign dimuon events in $b \bar{b}$ production in general left-right models without imposing manifest or pseudo-manifest left-right symmetry. We find the allowed region of new physics parameters satisfying the current experimental data.
The D0 Collaboration has reported an anomalous charge asymmetry in the production of same-sign muon pairs at the Fermilab Tevatron. The magnitude of this effect depends on the subtraction of several backgrounds, the most notable of which is due to kaons being misidentified as muons either through decays in flight or punch-through. The present authors suggested a check on such backgrounds consisting of a tight restriction on the muon impact parameter $b$, to confirm that this excess was indeed due to $B_{(s)}$ meson decays. The D0 Collaboration has performed a related check applying transverse …
Experimentally, the production of oppositely charged dimuon events by neutrino and anti-neutrino deep inelastic scattering (DIS) is used to determine the strangeness asymmetry inside a nucleon. Here we point out that the direct production of $D$-meson in DIS may make substantial influence to the measurement of nucleon strange distributions. The direct $D$-meson production is via the heavy quark recombination (HQR) and via the light quark fragmentation from perturbative QCD (LQF-P). To see the influence precisely, we compute the direct $D$-meson productions via HQR and LQF-P quantitatively and …
We study the new physics (NP) implications of the recently reported 3.2 sigma Standard Model (SM) deviation in the like-sign dimuon asymmetry at the Tevatron. Assuming that new physics only enters the B(s) mixing amplitude we explore the implications for generic new physics, general supersymmetric (SUSY) models and also SUSY SU(5). In the case of SUSY SU(5) we exploit the GUT scale relationship between slepton and squark soft masses to predict rates for lepton flavour violation (LFV). The predicted rates for tau --> mu + gamma are found to be detectable at future Super-B factories.
The measurement of a large like-sign dimuon asymmetry $A^b_{SL}$ by the D0 experiment at the Tevatron departs noticeably from Standard Model expectations and it may be interpreted as a hint of physics beyond the Standard Model contributing to $ΔB\neq 0$ transitions. In this work we analyse how the natural suppression of $A^b_{SL}$ in the SM can be circumvented by New Physics. We consider generic Standard Model extensions where the charged current mixing matrix is enlarged with respect to the usual $3\times 3$ unitary Cabibbo-Kobayashi-Maskawa matrix, and show how, within this framework, a sign…
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 compute the total cross section and the transverse momentum distribution for single charged slepton and sneutrino production at hadronic colliders including NLO supersymmetric and non-supersymmetric QCD corrections. The supersymmetric QCD corrections can be substantial. We also resum the gluon transverse momentum distribution and compare our results with two Monte Carlo generators. We compute branching ratios of the supersymmetric decays of the slepton and determine event rates for the like-sign dimuon final state at the Tevatron and at the LHC.
We give an assessment of the three approaches, undertaken by the D$\emptyset$ experiment, to probe CP violation in $B_s$ mixing without measurement of $B_s$-$\bar B_s$ oscillations or tagging: dimuon charge asymmetry $A_{SL}$, untagged single muon charge asymmetry $A_{SL}^s$, and lifetime difference in untagged $B_s \to J/ψϕ$ decay. The latter two approaches provide an alternative avenue, if not crosscheck, to the usual mixing-decay interference study in modes such as $B_s \to J/ψϕ$. Prospects at the Tevatron, LHC and (Super) B factories are discussed.
The D0 Collaboration has reported an excess of roughly one percent of $μ^- μ^-$ pairs over $μ^+ μ^+$ pairs in $\bar p p$ collisions at a center-of-mass energy $\sqrt{s} = 1.96$ GeV at the Fermilab Tevatron, when known backgrounds are subtracted. This excess, if ascribed to CP violation in meson-antimeson mixing of non-strange or strange neutral $B$ mesons, is about 40 times that expected in the Standard Model (SM). We propose a null test, based on a tight restriction on the muon impact parameter $b$, to confirm that this excess is indeed due to $B$ mesons. If the asymmetry is due to anomalous …
An analysis from the D0 Collaboration measuring the charge asymmetry A^b_sl of like-sign dimuon events due to semileptonic b-hadron decays at the Fermilab Tevatron Collider is described. It differs by 3.2 standard deviations from the Standard Model prediction to provide first evidence of CPT-invariant anomalous CP violation in the mixing of neutral B mesons, and is compared to the CP-violating phase obtained from a D0 analysis of the time-dependent decay angles in B0_s -> J/psi phi. If CPT violation is allowed, the dimuon asymmetry also yields the first sensitivity to CPT violation in the B0_s…
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 discuss effects induced by beyond leading order contributions to photon pair production. We point out that next to leading order contributions to the fragmentation component of the signal lead to a change in the shape of distributions. This is already mildly visible in present Tevatron data though stringent isolation criteria tend to suppress the fragmentation component considerably. We expect the effect to be experimentally confirmed in future data samples with higher statistics which would serve as a precision test for QCD.
We present a calculation of the D^{*+}, D^+ and D^0 meson single inclusive production cross section for the Tevatron Run II. We use the FONLL approach in perturbative QCD, which, besides including the known next-to-leading order corrections, also provides for the resummation at the next-to-leading logarithmic level of terms enhanced at large p_T by powers of log(p_T/m), where m is the charm mass and p_T is its transverse momentum. Non-perturbative effects in charm hadronization are extracted, in moment space, from recent ALEPH data for D^* fragmentation in e^+e^- collisions.
H1 Collaboration recently observed the charmed pentaquark. In this short note, we point out that the dominant production mechanism for pentaquark consisting of a heavy quark is heavy quark fragmentation. We obtain a crude estimate on the fragmentation probability for charm quark into Theta_c^0, based on the known fragmentation probabilities of charm quark into mesons and baryons: f(c-bar --> Theta_c^0) =~ (2-7) x 10^{-3}. Similarly, we also obtain the fragmentation probability for bottom quark into Theta_b^+: f(b-bar --> Theta_b^+) =~ (5-20) x 10^{-3}. We also estimate the prospect of observin…
We study the inclusive hadrodroduction of D^0, D^+, D^{*+}, and D_s^+ mesons at next-to-leading order in the parton model of quantum chromodynamics endowed with universal non-perturbative fragmentation functions (FFs) fitted to e^+e^- annihilation data from CERN LEP1. Working in the general-mass variable-flavor-number scheme, we resum the large logarithms through the evolution of the FFs and, at the same time, retain the full dependence on the charm-quark mass without additional theoretical assumptions. In this way, the cross section distributions in transverse momentum recently measured by th…
We review a recent global analysis of inclusive single-charged-hadron production in high-energy colliding-beam experiments, which is performed at next-to-leading order (NLO) in the parton model of quantum chromodynamics endowed with nonperturbative fragmentation functions (FFs). Comparisons of p p-bar data from CERN S p p-bar S and the Fermilab Tevatron and gamma p data from DESY HERA with the corresponding NLO predictions allow for quantitative tests of the scaling violations in the FFs and their universality. We emphasize the potential of new measurements at the Tevatron to place tight const…
The asymmetry of $D^-$ and $D^+$ meson production in $π^-N$ scattering observed by the E791 experiment is a typical phenomenon known as the leading particle effect in charm hadroproducton. We show that the phenomenon can be explained by the effect of light quark fragmentation into charmed hadrons (LQF). Meanwhile, the size of the LQF effect is estimated from data of the E791 experiment. A comparison is made with the estimate of the LQF effect from prompt like-sign dimuon rate in neutrino experiments. The influence of the LQF effect on the measurement of nucleon strange distribution asymmetry f…
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…
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.
We discuss the excess in the hadroproduction of B mesons at the Tevatron. We show that an accurate use of up-to-date information on the B fragmentation function reduces the observed excess to an acceptable level. Possible implications for experimental results reporting bottom quark cross sections, also showing an excess with respect to next-to-leading order theoretical predictions, are discussed.
CDF recently measured the quantity $\frac{σ(B_c^+)}{σ(B^+)} \frac{{\rm BR}(B_c^+ \to J/ψ\ell^+ ν)}{{\rm BR}(B^+ \to J/ψK^+)}$, {}from which we determine the ratio $\frac{σ(B_c^+)}{σ(\bar b)}$ to be $(2.08\err{1.06}{0.95})\times 10^{-3}$. In this note, we show that the ratio $\frac{σ(B_c^+)}{σ(\bar b)}$ obtained by dividing the $σ(B_c^+)$ by the leading order $σ(\bar b)$ is consistent with this derived CDF measurement. We calculate the cross section $σ(B_c^+)$ using the perturbative QCD fragmentation functions of Braaten, Cheung, and Yuan and the corresponding induced gluon fragmentation functi…
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 compare the transverse momentum (p_T) distribution of inclusive light-charged-particle production measured by the CDF Collaboration at the Fermilab Tevatron with the theoretical prediction evaluated at next-to-leading order in quantum chromodynamics (QCD) using fragmentation functions recently determined through a global data fit. While, in the lower p_T range, the data agree with the prediction within the theoretical error or slightly undershoot it, they significantly exceed it in the upper p_T range, by several orders of magnitude at the largest values of p_T, where perturbation theory sh…
Fragmentation functions for heavy-light mesons, like the charmed D, D^* mesons, are proposed. They rest on next-to-leading QCD Perturbative Fragmentation Functions for heavy quarks, with the addition of a non-perturbative term describing phenomenologically the quark --> meson transition. The cross section for production of large p_T D, D^* mesons at the Tevatron is evaluated in this framework.
We present next-to-leading order predictions for the production of triphoton final states at the LHC and the Tevatron. Our results include the effect of photon fragmentation for the first time and we are able to quantify the impact of different isolation prescriptions. We find that calculations accounting for fragmentation effects at leading order, and those employing a smooth cone isolation where no fragmentation contribution is required, are in reasonable agreement with one another. However, larger differences in the predicted rates arise when higher order corrections to the fragmentation fu…
We study J/psi photoproduction via fragmentation at next-to-leading order in the QCD-improved parton model, using the nonrelativistic factorization formalism proposed by Bodwin, Braaten, and Lepage. We consider direct and resolved photoproduction of prompt J/psi mesons and chi_{cJ} mesons radiatively decaying to J/psi+gamma, taking into account the formation of both color-singlet and color-octet c anti-c states. Adopting the values of the long-distance color-octet matrix elements extracted from fits to prompt-J/psi data recently taken at the Fermilab Tevatron, we predict that measurements of J…
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。
A D0 analysis measuring the charge asymmetry Ab_sl of like-sign dimuon events due to semileptonic b-hadron decays at the Fermilab Tevatron Collider has shown indications of possible anomalous CP violation in the mixing of neutral B mesons. This result has been used to extract the first senstivity to CPT violation in the B0_s system. A procedure to explore further this anomaly by specifically measuring the semileptonic charge asymmetry, as_sl, in B0_s decays is described, as well as how a variant of this analysis can be used to explore a larger set of CPT-violating parameters in the B0_s system…
We re-analyze the direct $\jp$ production processes at the Fermilab Tevatron in view of the recent observation at the B-factories, where both $\jp$ inclusive and exclusive production rates are found to be about an order of magnitude larger than the leading order estimates of non-relativistic QCD. The charm quark fragmentation to $\jp$, which is the dominant color-singlet process at high $p_T$, is normalized by the B-factory measurements. The process receives further enhancement due to the charm sea contribution which has so far been ignored in most analyses. After summing up all sub-process co…
The transverse momentum ($p_t$) distributions of production and polarization for $J/ψ$ measured by CDF Collaboration are still challenging our understanding of the heavy quarkonium production mechanism even with recent significant theoretical progresses on the next-to-leading-order (NLO) QCD calculation. We suggest a new mechanism for $J/ψ$ production at hadron collider, $pp(\bar p)\to γ^{\ast}(J/ψ)+X$ with $J/ψ$ from a virtual photon $γ^{\ast}$ fragmentation. Our calculations show it's $p_t$ distribution at NLO will be larger than that of the conventional $J/ψ$ production from the color-singl…
We provide nonperturbative fragmentation functions for B mesons, both at leading and next-to-leading order in the MS-bar factorization scheme with five massless quark flavors. They are determined by fitting the fractional energy distribution of B mesons inclusively produced in e^+ e^- annihilation at CERN LEP1. Theoretical predictions for the inclusive production of B mesons with high transverse momenta in p p-bar scattering obtained with these fragmentation functions nicely agree, both in shape and normalization, with data recently taken at the Fermilab Tevatron.
We present a calculation of the leading order QCD fragmentation functions for gluons to split into spin-triplet D-wave quarkonia. We apply them to evaluate the gluon fragmentation contributions to inclusive ^3D_J quarkonium production at large transverse momentum processes like the Tevatron and find that the D-wave quarkonia, especially the charmonium 2^{--} state, could be observed through color-octet mechanism with present luminosity. Since there are distinctively large gaps between the contributions of two different (i.e, color-singlet and color-octet) quarkonium production mechanisms, our …
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 inclusive hadroproduction of D^0, D^+, D^star+, and D_s^+ mesons at leading order in the parton Reggeization approach endowed with universal fragmentation functions fitted to $e^+e^-$ annihilation data from CERN LEP1. We have described $D$-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Tevatron (|y|<1) and ALICE Collaboration at LHC (|y|<0.5) within uncertainties and without free parameters, using Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward D-meson production (|y|>2.0) measur…
We use the NRQCD factorization formalism to calculate the relativistic corrections to the fragmentation function for a gluon fragmenting into a spin-triplet S-wave heavy quarkonium. We make use of the gauge-invariant formulation of the fragmentation function of Collins and Soper. The color-octet contribution receives a large, negative relativistic correction, while the color-singlet contribution receives a large, positive relativistic correction. The considerable decrease in the color-octet contribution requires a corresponding increase in the phenomenological value of the leading color-octet …
We study the inclusive hadroproduction of $B^0$, $B^+$, and $B_s^0$ mesons at leading order in the parton Reggeization approach using the universal fragmentation functions extracted from the combined $e^+e^-$ annihilation data from CERN LEP1 and SLAC SLC colliders. We have described $B$-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Fermilab Tevatron and CMS Collaboration at LHC within uncertainties and without free parameters, applying Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward $B$-meso…
Hadronic Production of S-wave and P-wave Charmed Beauty Mesons via Heavy Quark Fragmentation
在强子对撞机上，具有大横向动量的$(\bar bc)$介子的主要产生机制是部分子碎裂。计算了Tevatron中通过底反夸克直接碎裂和Altarelli-Parisi诱导胶子碎裂产生S波和P波$(\bar b c)$介子的速率和横动量谱.由于所有的径向和轨道激发的$(\bar b c)$介子低于$BD$味阈值将级联到赝标基态$B_c$通过电磁和/或强子跃迁，他们都有助于包括生产$B_c$。激发S波和P波态对$B_c$的贡献分别为58%和23%，因此是显著的.
This paper describes the first measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron Collider at Fermilab. The result is based on a 360 pb-1 sample of data collected with the CDF II detector in p-pbar collisions at sqrt{s}=1.96 TeV. Semileptonic decays of B0, B+, and B_s mesons, as well as Lambda_b baryons, are reconstructed. For an effective bottom hadron p_T threshold of 7 GeV/c, the fragmentation fractions are measured to be f_u/f_d=1.054 +/- 0.018 (stat) +0.025-0.045(sys) +/- 0.058 (Br), f_s/(f_u+f_d)=0.160 +/- 0.005 (stat) +0.011-0.010 (sys) +0.057-0…
The full order $α_s^4$ perturbative QCD calculation of the production of $B_c$ mesons at the Tevatron is compared with the fragmentation approximation. The non-fragmentation diagrams, in which two or more quarks and/or gluons can simultaneously be nearly on-shell, are important unless $P_T\gg M_{B_c}$.
Theoretical analyses of the results on quarkonium production at large transverse momentum ($p_T$) in $p\bar p$ collisions, at the Tevatron have revealed two novel features of the physics of quarkonium production : 1) the contribution of fragmentation of gluons and charm quarks to the cross-section at large $p_T$, and 2) the importance of colour octet components of the quarkonium wave-function. I discuss the theoretical developments which have contributed to a reasonably consistent picture of quarkonium production at the Tevatron, and discuss large-$p_T$ $J/ψ$ production at HERA and at LHC as i…
We present a Monte-Carlo approach to prompt-photon production, where photons and QCD partons are treated democratically. The photon fragmentation function is modelled by an interleaved QCD+QED parton shower. This known technique is improved by including higher-order real-emission matrix elements. To this end, we extend a recently proposed algorithm for merging matrix elements and truncated parton showers. We exemplify the quality of the Monte-Carlo predictions by comparing them to measurements of the photon fragmentation function at LEP and to measurements of prompt photon and diphoton product…
