Meson Research Articles

A Conversation with Robert F. Christy – Part II

Robert F. Christy, Institute Professor of Theoretical Physics Emeritus at Caltech, recalls his wartime work at Los Alamos on the critical assembly for the plutonium bomb (“the Christy bomb”); the Alamogordo test, July 16, 1945; the postwar concerns of ALAS (Association of Los Alamos Scientists); his brief return to the University of Chicago and move to Caltech; friendship with and later alienation from Edward Teller; work with Charles and Tommy Lauritsen and William A. Fowler in Caltech’s Kellogg Radiation Laboratory; Freeman Dyson’s Orion Project; work on the meson and RR Lyrae stars; fellowship at Cambridge University; 1950s Vista Project at Caltech; his opposition to the Strategic Defense Initiative; and his post-retirement work for the National Research Council’s Committee on Dosimetry and on inertial-confinement fusion.

Measurement of interference between electromagnetic and strong amplitudes inψ(2S)decays to two pseudoscalar mesons

Using a sample of 3.08 million psi(2S) decays collected at sqrt{s} = 3.686 GeV with the CLEO detector at the Cornell Electron Storage Ring, we have measured the branching fractions for psi(2S) decays to pseudoscalar pairs pi+pi-, K+K-, and KsKl. We obtain B(psi(2S) -> pi+pi-) < 2.1 x 10^{-5} (90% C.L.), B(psi(2S) -> K+K-) = (6.3 +- 0.6(stat) +- 0.3(syst)) x 10^{-5}, and B(psi(2S) -> KsKl) = (5.8 +- 0.8(stat) +- 0.4(syst)) x 10^{-5}. The branching fractions allow extraction of the relative phase Delta = (95 +- 15) degrees and strength ratio R = (2.5 +- 0.4) of the three-gluon and one-photon amplitudes for these modes.

RELATIVISTIC FIVE-QUARK EQUATIONS AND u, d-PENTAQUARK SPECTROSCOPY

The relativistic five-quark equations are found in the framework of the dispersion relation technique. The five-quark amplitudes for the low-lying pentaquarks including u, d quarks are calculated. The poles of the five-quark amplitudes determine the masses of the ududţ and uuuuţ pentaquarks. The calculated of pentaquark amplitudes estimates the contributions of four subamplitudes. The main contributions to the pentaquark amplitude are determined by the subamplitudes, which include the meson states M.

CLASSIFICATION OF THE SCALAR MESONS: A STRANGE POLE EXPEDITION INTO CHARM AND BEAUTY TERRITORY

The classification of scalar and vector mesons is reviewed within the framework of the Resonance-Spectrum Expansion (RSE). This method allows a simple and straightforward description of non-exotic meson–meson scattering, incorporating the effects of quark confinement and OZI-allowed decay in a fully nonperturbative way. Results for resonances and bound states are compared to experiment, on the basis of computed pole positions and cross-sections. New predictions for open-charm and -bottom scalar mesons are presented.Concretely, observed vector states for [Formula: see text] and [Formula: see text] are reproduced, and others are predicted. In the light scalar sector, the now established two nonets, one below 1 GeV and one in the region 1.3–1.5 GeV, are easily described, through the appearance of extra poles in the S-matrix. The recently found [Formula: see text](2317) meson is accurately reproduced by the same mechanism, as a quasi-bound state in the coupled [Formula: see text] system.In S-wave Dπ and Bπ scattering, new resonances are foreseen close to threshold, i.e. a [Formula: see text] at 2.16±0.05 GeV some 250 MeV wide, and a [Formula: see text] at 5.47±0.05 GeV with a width of about 50 MeV. Additional predictions concern the existence of [Formula: see text] and [Formula: see text] scalar mesons, stable with respect to OZI-allowed decay to BK and BD, respectively, namely at 5.61±0.05 GeV resp. 6.64±0.05 GeV.

The PHENIX measurement of heavy flavour via single electrons in pp, d–Au and Au–Au collisions at

The PHENIX experiment at RHIC has measured single electron spectra in proton–proton, deuteron–gold and gold–gold collisions at . The photonic contribution (photon conversions and Dalitz decays) is subtracted from the inclusive spectra resulting in non-photonic single electron spectra. The principal source of non-photonic electrons is the semi-leptonic decay of charm and bottom mesons. The implications for heavy flavour production in hot and cold nuclear systems are discussed.

RICH counters for b-experiments

The paper reviews the motivation and status of ring imaging Cerenkov (RICH) counters for Belle and BaBar, experiments at e+e– B-factories, as well as their upgrades. PACS: 29.40.Ka Cherenkov detectors – 13.25.Hw Decays of bottom mesons

Prospects for pentaquark production at meson factories

Following Rosner [hep-ph/0312269], we consider B-decay production channels for the exotic I=0 and I=3/2 pentaquarks that have been recently reported. We also discuss new search channels for isovector pentaquarks, such as the Θ∗++(s̄duuu), that are generically present in chiral soliton models but were not observed in recent experiments. Furthermore, we argue that weak decays of charmed baryons, such as the Λc+ and Ξc0, provide another clean way of detecting exotic baryons made of light quarks only. We also discuss discovery channels for charmed pentaquarks, such as the isosinglet Θc0(c̄udud), in weak decays of bottom mesons and baryons. Finally, we discuss prospects for inclusive production of pentaquarks in e+e− collisions, with associated production of particles carrying the opposite baryon number.

Results on CP violation from CDF

The CDF experiment at the Tevatron collider is collecting a large sample of fully hadronic decays of Bottom and Charm mesons. First CP Violation measurements have been performed using the initial data, achieving results which clearly state the CDF ability in extracting significant CKM information from p{bar p} collisions. The first results on direct CP asymmetries on Charm and Bottom decays and future plans from the CDF experiment are discussed in this paper.

Time-dependent CP violation in B0→ K0 s φ, $K^0_s\eta'$ and K0 s K+ K– in the Belle and BaBar experiments

Both the Belle and BaBar collaborations have recently measured time-dependent CP violation in B0 decays to $ss\overline{s}$ states and compared the results to those for $sc\overline{c}$ states for which quite precise results were previously available. Within the framework of the standard model the same results should be expected for both cases. The decays to $ss\overline{s}$ states are dominated by penguin diagrams and may be sensitive to physics beyond the standard model. For these states, compared to the results for $sc\overline{c}$ states, a discrepancy in the mixing-induced CP violation of 2.7 standard deviations was found, and may be interpreted as an indication for physics beyond the standard model. PACS: 11.30.Er Charge conjugation, parity, time reversal, andother discrete symmetries – 12.15.Hh Determination of Kobayashi-Maskawa matrix elements – 13.25.Hw Decays of bottom mesons

Testing the standard model with B→ (K*,ρ) γ decays

We review the theory and phenomenology of B→ (K*,ρ) γ decays. The impact of these decay modes on the determination of the CKM angles is investigated. Taking into account most recent experimental data and theoretical inputs, we present an updated analysis of the constraints induced onto the $(\bar \rho,\bar \eta)$ plane. PACS: 13.20.H2Decays of bottom mesons – 12.38.CySummation of perturbation theory

Rare hadronic B decays from BaBar

A selection of rare decay results from BaBar are presented, from a data sample of 82fb–1 of data taken at the Υ (4S) resonance (corresponding to 88× 106 $B\overline{B}$ pairs). PACS: 13.25.Hw Decays of bottom mesons

|V cb |, |V ub |, and HQET at CLEO

I report results from the CLEO collaboration on semileptonic B decays, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements |V cb | and |V ub |. I describe the techniques used to obtain the recent improvements in precision for these measurements, including the use of the b→ sγ photon spectrum to reduce hadronic uncertainties in semileptonic B decays. I also report new measurements of |V cb | using the inclusive semileptonic branching fraction ${\cal B}(B\to X e \nu)$ and of |V ub | through study of the q2 dependence of B→πℓν and B→ρℓν. PACS: 12.15.Hh Determination of Kobayashi-Maskawa matrix elements – 13.20.He Decays of bottom mesons

Charmless B decays from CLEO: Rare and not-so-rare

We present updated results from the CLEO collaboration from two studies of B meson decay to charmless hadronic final states. In the first analysis, we combine data from the CLEO II and CLEO III detectors to provide final measurements of thirteen two-body decay modes. In the second, the combined CLEO II and CLEO II.V data set is used to determine the $\eta'$ momentum spectrum and branching ratio in the inclusive process $B\to \eta' X_{nc}$ ; with a more powerful analysis technique than was previously used. For the momentum range $2.0<P_{\eta'}< 2.7$ GeV/c , we find a branching ratio, ${\cal B}(B \to \eta'X_{nc})$ , of [4.6± 1.1± 0.4± 0.5] × 10–4. The uncertainties are statistical, systematic, and due to subtraction of charm-decay background, respectively. PACS: 13.25.Hw Decays of Bottom Mesons

Status of lattice calculations of B-meson decays and mixing

The present status of lattice calculations of fB, BB and SU(3) flavour breaking ratios such as ${f_{\rm B_s}}/{f_{\rm B}}$ is reviewed. Particular attention is devoted to systematic uncertainties, such as those arising from the lack of simulation data for dynamical quarks with realistic masses, and the related difficulties associated with chiral extrapolations. Global averages for decay constants and mixing parameters are presented (Table 1), and the procedures to obtain them are discussed in detail. PACS: 11.30.Er CP violation – 12.38.Gc Lattice QCD calculations – 14.40.Nd Bottom mesons

Indications for large rescattering in rare B decays

The sign of ACP(K–π+) < 0, the evidence for $\bar B^0 \to \pi^0\pi^0$ , and the possibly sizable A π π and S π π in $\bar B^0 \to \pi^+\pi^-$ all suggest that final state rescattering may be needed in $\bar B\to PP$ decay, which is echoed by large color suppressed $\bar B^0\to D^0h^0$ modes. An SU(3) formalism of $\mbox{\bf 8}\otimes \mbox{\bf 8} \to \mbox{\bf 8}\otimes \mbox{\bf 8}$ rescattering in PP final states leads to interesting predictions, in particular allowing for small $\bar B^0 \to K^-K^+$ . PACS: 11.30.Hv Flavor symmetries – 13.25.Hw Decays of bottom mesons

B decays into charm at CLEO

Recent measurements of the branching fractions and helicity amplitudes of the decays B–→ D⋆ 0 ρ– and ${\bar B}^0 \to D^{\star +} \rho^{-}$ by the CLEO collaboration are presented. The fraction of longitudinal polarization in the ${\bar B}^0 \to D^{\star +} \rho^{-}$ decay is found to be consistent with the factorization hypothesis, although the helicity amplitudes show evidence for nonzero final-state interaction phases. PACS: 13.25.Hw Decays of bottom mesons – 12.39.St Factorization – 14.40.Nd Bottom mesons

Rare B → baryon decays from CLEO

We have searched for baryon-containing radiative penguin decays in 9.7 × 106 $B\bar{B}$ events collected at the Υ(4S) with the CLEO detector. We find no evidence for such decays, and set a 90% confidence level upper limit of ${\cal B} (B \rightarrow X_s \gamma, X_s ~{\it containing~baryons}) _{E_\gamma > 2.0 \rm{~GeV}} < 3.8 \times 10^{-5}$ . Corrections to CLEO’s recent b → s γ measurement due to $B \rightarrow X_s({\it baryon}) \gamma$ decays are well within the errors quoted. A search for semileptonic decays of B mesons to $e\bar{p}$ inclusive final states in the same data sample found no evidence for such decays and set an upper limit of ${\cal B} (B \rightarrow \bar{p} e^- \bar{\nu}_e X) < 5.9 \times 10^{-4}$ . These limits suggest that external W emission is not the dominant source of baryon production in B decay. PACS: 13.20.HeDecays of Bottom Mesons – 13.40.HqElectromagnetic Decays – 13.60.RjBaryon Production

Enhancement of φ meson production in p-p and Pb-Pb collisions at SPS energy

The φ meson yield, rapidity and transverse mass distributions in p-p and Pb-Pb collisions at 158 A GeV were studied by the hadron-string cascade model, LUCIAE. By adjusting the width parameter in q\(\bar q\) Gaussian like transverse momentum distribution in string fragmentation to fit the NA49 data of φ meson transverse mass distribution in p-p collisions, the obtained φ meson rapidity distribution in p-p collisions, the rapidity and transverse mass distributions in Pb-Pb collisions, and the φ meson enhancement factor in Pb-Pb relative to p-p collisions were compatible with corresponding NA49 data, which might be attributed to the collective effect in gluon emission of string and the reduction of strange quark suppression mechanisms involved in the LUCIAE model

Weak decays of heavy mesons in a covariant quark model

In this paper we investigate weak decays of heavy mesons in the framework of a covariant quark model, which is based on the Bethe-Salpeter equation in instantaneous approximation. Apart from a phenomenological confinement potential, a residual interaction induced by instantons is adopted. Masses and many decay observables of light mesons have already been described successfully in this model (Eur. Phys. J. A 9, 73 (2000); 221). An appropriate extension allows a unified description of light and heavy systems. Using a set of parameters, which are fixed by the mass spectra, we evaluate the form factors of semileptonic decays of charmed and bottom mesons. In the heavy-quark limit these can be reduced to the Isgur-Wise function, which is calculated. Finally, the form factors are used to determine the non-leptonic decay rates of B-mesons in the factorization approximation.

Search for the familon via B± → π±X0, B± → K±X0, and B0 → Ks0X0 decays

We have searched for the two-body decay of the B meson to a light pseudoscalar meson h = π γ , K γ , K 0 S and a massless neutral feebly interacting particle X° such as the familon, the Nambu-Goldstone boson associated witha spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 X 10 6 BB mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set 90% C.L. upper limits B(B γ → h γ X 0 ) = 4.9 X 10 - 5 and B(B 0 → K 0 S X 0 ) = 5.3 × 10 - 5 . These limits correspond to a lower bound of approximately 10 8 GeV on the family symmetry breaking scale with vector coupling involving the third generation of quarks.