We report on recent results in spectroscopy from BaBar. This includes the
discovery of a new $\Lambda_c$ baryon, detailed studies of the
$D^*_{sJ}(2317)^+$, $D_{sJ}(2460)^+$, X(3872) and Y(4260) particles and the
first measurement of hadronic non-$B\bar{B}$ decays of the $\Upsilon(4S)$
meson.Comment: 4 pages (5 here), to appear in Proceedings of the XLIst Rencontres de
  Moriond, QCD and Hadronic Interactions, La Thuile, Italy, 18-25 March 200

/SLAC

Gowdy, S.J.

English

arXiv

We report on recent results in spectroscopy from BABAR. This includes the discovery of a new {Lambda}{sub c} baryon, detailed studies of the D*{sub sJ}(2317){sup +}, D{sub sJ}(2460){sup +}, X(3872) and Y(4260) particles and the first measurement of hadronic non-B{bar B} decays of the {Upsilon}(4S) meson

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Work supported in part by Department of Energy contract DE-AC02-76SF00515QUARKONIUM AND CHARM HADRONS : NEW RESULTS ONSPECTROSCOPY IN BABARS.J. GOWDY FOR THE BABAR COLLABORATIONStanford Linear Accelerator Center, 2575 Sand Hill Rd, Menlo Park CA 94025, USAWe report on recent results in spectroscopy from BABAR. This includes the discovery of a newΛc baryon, detailed studies of the D∗sJ(2317)+, DsJ(2460)+, X(3872) and Y(4260) particlesand the first measurement of hadronic non-BB decays of the Υ(4S) meson.1 BABARThe BABAR detector is described in detail in a prior publication 1.2 Charm Baryon SpectroscopyThe current particle assignment by the Particle Data Group 2 is assigned indirectly rather thanbeing based on angular analysis. The Λc(2785) and Λc(2880) states 3 are only listed as single ordouble asterisk (respectively) as they have not yet been confirmed.In studying the D0p spectra BABAR has observed two charm baryons4, the Λc(2880) and theΛc(2940). The data sample in this study was 288 fb−1. The D0 was found from its decay toeither K−π+ or K−π+π−π+. No signal for these particles was seen in the D+p mode which rulesout a Σc states.The observation of these particles in this channel rules out some other non-Λc interpretations5;Σc2(32 ,52), Λ′c1(32) and Λ′c2(32 ,52).The first of these is the Λc(2880), confirming CLEO’s discovery 3. The particle’s parametersfound in this analysis are;m = [ 2881.9 ± 0.1 (stat.) ± 0.5 (syst.) ] MeV/c2Γ = [ 5.8 ± 1.5 (stat.) ± 1.1 (syst.) ] MeV .SLAC-PUB-11869June 2006Invited talk presented at 41st Rencontres De Moriond: QCD And Hadronic Interactions,3/18/2006--3/25/2006, La Thuile, ItalyTable 1: A summary of the combined mass and width results. For the masses, the first quoted uncertainty isstatistical and the second is systematic. The limits on the intrinsic width Γ are at 95% CL.Particle Mass (MeV/c2) Γ (MeV)D∗sJ(2317)+ 2319.6± 0.2± 1.4 < 3.8DsJ(2460)+ 2460.1± 0.2± 0.8 < 3.5Ds1(2536)+ 2534.6± 0.3± 0.7 < 2.5A new baryon has been discovered with the properties;m = [ 2939.8 ± 1.3 (stat.) ± 1.0 (syst.) ] MeV/c2Γ = [ 17.5 ± 5.2 (stat.) ± 5.9 (syst.) ] MeV .This state has been given the name Λc(2940)+. There is no evidence of doubly-chargedpartners in the D+p spectrum.3 Charm Meson SpectroscopyCurrent theory of treating cs system like the hydrogen atom (with one heavy and one lightelement) has been fairly successful. Prior to 2003 this theory had postulated many particlesthat were later observed as expected. A few expected states were not observed and this wasascribed to their predicted large widths.The D∗sJ(2317)+ was discovered by BABAR6. CLEO published7 the discovery of the DsJ(2460)+.An extensive study of decays to D+s plus one or two particles of the types π±, π0 or γ hasbeen carried out8 looking at 232fb−1 of data.The D+s was reconstructed from only K+K−π+ decays. Furthermore to reduce background,only certain intermediate states were allowed: either a φ(1020) could be reconstructed from theK+K− or a K∗(892) from K−π+.Only three decay modes are measured (the rest only have upper limits reported in thisanalysis). The ratio of the measured branching fractions are;B(DsJ (2460)+→D+s γ)B(DsJ (2460)+→D+s π0γ)= 0.337± 0.036± 0.038B(DsJ (2460)+→D+s π+π−)B(DsJ (2460)+→D+s π0γ)= 0.077± 0.013± 0.008The decays seen are consistent with both particles being P-wave cs mesons with the D∗sJ(2317)+being 0+ and the DsJ(2460)+ being 1+ states. The particle properties measured in this analysisare shown in Table 1. It should be noted that no intrinsic width is measured.No evidence was found for doubly-charged or neutral partners of the D∗sJ(2317)+. Thisdeficit disfavours some molecule interpretations of these states.The fully reconstructed B sample was used to also study twelve decay modes of neutral andcharged B mesons of the form D(∗)s(J)D(∗). In this sample the properties of the the B mesons arewell known due to all decay products of one of the B mesons being measured. This analysisused 230 million BB pairs9.All decay products of one of the D mesons are also measured, the other D could decay toanything and is represented as DX , its mass and momenta inferred by kinematics. The massspectra of the DX system is studied in each of the modes to determine absolute branchingfractions.Using previously published10 BABAR study of the branching fraction for B→ DsJ(2460)+D(∗)it is possible to determine some absolute branching fractions;B(DsJ(2460)+ → D∗+s π0) = (56 ± 13stat. ± 9syst.) %B(DsJ(2460)+ → D+s γ) = (16 ± 4stat. ± 3syst.) %We therefore know that the DsJ(2460)+ decays via a photon or a π0 emission to a D(∗)+s(72 ± 19)% of the time. Also known from branching fraction ratios reported earlier in thissection together with this result that approximately another 4% emit a pair of charged pionswhile decaying to a D+s .4 Charmonium SpectroscopyThere are many models for Charmonium spectroscopy that predict as yet unseen particles11.Some of these may be the recently observed X(3872) and Y(4260) states.The X(3872) particle was discovered by Belle12 and confirmed by BABAR13. It is unknown ifit is a cc pair, diquark-antidiquark pair or a D0D∗0 molecule.The diquark model would predict that the X(3872) is actually two amplitudes of a nonet, onevisible via charged and other via neutral B mesons decays. The predicted mass difference of theXu and Xd states is 7±2 MeV/c2. The difference has been measured14 to be 2.7±1.3±0.2 MeV/c2.This is consistent with both the prediction and zero.Some molecules models predict that the ration of these branching fractions should be lessthan 10%. The measurement shows the ratio to be between 0.13 and 1.10 at the 90% confidencelevel, so those models are disfavoured.Belle has reported evidence15 of the decay X(3872)→ J/ψγ in B meson decays. An analysishas been done using 287 million BB decays to confirm this. The following branching fraction wasalso measured to validate signal extraction method and is found to agree with the the ParticleData Group value;B(B+ → χc1K+) = (5.6± 0.2± 0.7)× 10−4The analysis finds 19.2± 5.7 events and a product branching fraction of;B(B+ → X(3872)K+,X(3872)→ J/ψγ) = (3.4± 1.0± 0.3)× 10−6The observation of this mode implies that the X(3872) is a C=+1 state. The partial widthratio has also been measured to be;Γ(X(3872)→ J/ψγ)Γ(X(3872)→ J/ψπ+π−)= 0.34± 0.14232fb−1 of initial state radiation (ISR) data has been studied looking for the X(3872) butno evidence was found. This unsuccessful search for X(3872) resulted in the discovery of theY(4260)16. This state has been confirmed by CLEO17.A study has been carried out on 232 million BB decays14. This study shows a consistentfeature with the discovery spectra and measures a product branching fraction of;B(B− → Y(4260)K−,Y(4260)→ J/ψπ+π−) = (2.0± 0.7± 0.2)× 10−5An analysis of 232fb−1 of ISR data using the final state K+K−π+π− has been carried out,in this analysis the ISR photon was observed. Events are selected where the kaon pair comesfrom a φ to provide a confidence limit (CL);B(Y(4260)→ φπ+π−).ΓYee < 0.4eV at 90% CLA recent BABAR result16 can be use to obtain the ratio of branching fractions;B(Y(4260)→ φπ+π−)B(Y(4260)→ J/ψπ+π−)< 0.102 at 90% CLThe glueball hypothesis predicts18 these to be equal, therefore it is disfavoured.5 Bottomonium SpectroscopyDecays of the Υ states above the BB have been primarily to that state. BABAR has now measuredsome non-BB hadronic decays of the Υ(4S).This analysis19 used (230.0 ± 2.5) × 106Υ(4S) decays, which corresponds to 211fb−1 of on-peak data. As a cross check another 22fb−1 of off-peak data (approximately 40MeV below theΥ(4S) peak) was searched for for any indications of Υ(4S) decays and none were found.The decays being searched for are Υ(4S) → Υ(nS)π+π−, with n=1,2. The Υ(nS) statesare reconstructed from oppositely charged pairs of electrons or muons. However, due to highbackground from Bhabha events only the muon decays are used in the measurement. Theelectron sample is use as a cross check.The branching fractions obtained by using the Particle Data Group’s averages forB(Υ(nS)→µ+µ−);B(Υ(4S)→ Υ(1S)π+π−) = (0.90 ± 0.15) ×10−4B(Υ(4S)→ Υ(2S)π+π−) = (1.29 ± 0.32) ×10−46 SummaryA new charmed baryon has been observed. In addition, for the first time a decay of a charmbaryon to a non-charm baryon has been measured. Many enhancements to the knowledge ofthe D∗sJ(2317)+, DsJ(2460)+, X(3872) and Y(4260) particles have been accomplished. We havereported on the first measurement of hadronic non-BB decays of the Υ(4S) meson.References1. B. Aubert et al., Nucl. Instrum. Methods A 479, 1-116 (2002).2. S. Eidelman et al., Phys. Lett. B 592, 1 (2004).3. M. Artuso et al., Phys. Rev. Lett. 86, 4479 (2001).4. B. Aubert et al., Submitted to Phys. Rev. Lett., hep-ex/0603052.5. A.E. Blechman et al., Phys. Rev. D 67, 074033 (2003).6. B. Aubert et al., Phys. Rev. Lett. 90, 242001 (2003).7. D. Besson et al., Phys. Rev. D 68, 032002 (2003).8. B. Aubert et al., Submitted to Phys. Rev. D, hep-ex/0604030.9. B. Aubert et al., Submitted to Phys. Rev. D (Rapid Communications), hep-ex/0605036.10. B. Aubert et al., Phys. Rev. Lett. 93, 181801 (2004).11. T. Barnes, S. Godfrey and E.S. Swanson, Phys. Rev. D 72, 054026 (2005).12. S.K. Choi et al., Phys. Rev. Lett. 91, 262001 (2003).13. B. Aubert et al., Phys. Rev. D 71, 071103(R) (2005).14. B. Aubert et al., Phys. Rev. D 73, 011101 (2006).15. K. Abe et al., hep-ex/050537 (2005).16. B. Aubert et al., Phys. Rev. Lett. 95, 142001 (2005).17. T.E. Coan et al., Phys. Rev. Lett. 96, 162003 (2006).18. S. Zhu, Phys. Lett. B 625, 212 (2005).19. B. Aubert et al., Submitted to Phys. Rev. Lett., hep-ex/0604031.

Quarkonium and Charm Hadrons: New Results on Spectroscopy in BaBar

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Quarkonium and Charm Hadrons : New Results on Spectroscopy in BaBar

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