PoS(EPS-HEP2015)529. Charmed hadron decays at BESIII. Liaoyuan Dong Institute of High Energy Physics, Beijing , China

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1 Liaoyuan Dong Institute of High Energy Physics, Beijing 149, China I present here a selection of preliminary results on charmed hadron decays from BESIII collaboration, including study of D + K π + e + ν e, measurement of form factors in D + ωe + ν e search for D + φe + ν e, study of decay dynamics CP asymmetry in D + K L e+ ν e, measurements of absolute branching fractions of twelve Cabbibofavored hadronic Λ + c decay modes Λ + c Λe + ν e. The results are based on data samples collected with BESIII detector at ψ(77) peak at central-of-mass energy of GeV. The European Physical Society Conference on High Energy Physics 9 July 15 Vienna, Austria Speaker. on behalf of BESIII collaboration. This work is supported in part by National Natural Science Foundation of China (NSFC) under Contracts Nos , c Copyright owned by author(s) under terms of Creative Commons Attribution-NonCommercial-NoDerivatives 4. International License (CC BY-NC-ND 4.).

2 Liaoyuan Dong 1. Introduction Recent results from BESIII experiment based on.9 fb 1 recorded at ψ(77) peak 567 pb 1 at E cm = GeV are presented here for studies of charmed hadron decays. The ψ(77) predominantly decays to pairs of D mesons, eir D + D or D D. At E cm = GeV, Λ c mesons are primarily produced as Λ + c Λ c pairs. To identify D D/Λ + c Λ c pairs, we make use of double-tag technique initially used by MARK III [1]. In this technique, yields of single tags (ST), where one D/Λ c is reconstructed in tag modes, double tags (DT), where both D/Λ c mesons are reconstructed, are determined. In this report, D is reconstructed in one of six tag modes: D K + π π, K + π π π, KS π, KS π π, KS π π π +, K + K π, while Λ + c is reconstructed in one of twelve tag modes: Λ + c pks, pk π +, pks π, pks π+ π, pk π + π, Λπ +, Λπ + π, Λπ + π π +, Σ π +, Σ + π, Σ + π + π Σ + ω. The hadronic decays are identified using beam-constrained mass M BC Ebeam p c, where E beam is beam energy p is measured momentum of D or Λ c. The semileptonic decays are detected through kinematic variable U miss E miss c p miss, where E miss P miss are missing energy momentum carried by neutrino, respectively. Throughout this report, inclusion of charge conjugated processes is implied, unless orwise explicitly mentioned. In this proceeding, I report five preliminary measurements from BESIII collaboration. First I will present three results about D semileptonic decays, n present measurements of absolute branching fractions for twelve hadronic Λ + c decay modes, end this report with measurement of absolute branching fraction of Λ + c Λe + ν e.. D + K π + e + ν e (preliminary) The semileptonic decay D + K π + e + ν e provides a unique tool for investigating Kπ system, measuring K (89) resonance parameters hadronic transition form factors. Using double-tag technique, we select 186 cidate events measure branching fractions to be B(D + K π + e + ν e ) = (.71 ±. ±.8)% over full m Kπ range B(D + K π + e + ν e ) [.8,1] = (. ±. ±.7)% in K (89) region, respectively. We perform a partial wave analysis (PWA) on selected cidates. The probability density function (PDF) is expressed on five kinematic variables []: m (Kπ mass square), q (eν e mass square), θ K (angle between π D direction in Kπ rest frame), θ e (angle between ν e D direction in eν e rest frame), χ (angle between two decay planes). The q dependent helicity basis form factors are parameterized according to spectroscopic pole dominance (SPD) model, phase δ S of S-wave amplitude is parameterized as that used in LASS parameterization. The PWA shows that dominant component is K (89), S-wave contribution equal to (6.5 ±. ±.18)%, contributions from K (141) K (14) are negligible. Projections of five kinematic variables are shown in Fig. 1. We determine K (89) resonance parameters: m K (89) = (894.6±.5±.8) MeV/c, Γ K (89) = (46.4±.56 ±.15) MeV/c, Blatt-Weisskopf parameter r BW =.7 ±.6 ±.11 (GeV/c) 1. We also measure parameters defining hadronic form factors: r V = V () A 1 () = ±.58 ±.7, r = A () A 1 () =.788 ±.4 ±.8, m V = ( ±.) MeV/c (first measurement), m A = ( ±.) MeV/c, A 1 () =.585 ±.11 ±.17.

3 m V = ( ±.) MeV/c, m A = ( ±.) MeV/c, A 1 () =.585 ± Charmed.11 hadron ±.17. decays m V atisbesiii firstly measured for this decay. Corresponding projections Liaoyuan over Dong five kinematic variables are illustrated in Figure 1. /.GeV/c m Kπ (GeV/c ) data fit bg /.GeV/c m Kπ (GeV/c ) 4 /c /.5 GeV q (GeV /c 4 ) / cosθ e (degree) δ S / cosθ K /.4π χ Figure Figure 1: Projections 1: Projections of data (dots ontowith eacherror of bars) kinematic of PWA variables, solution comparing (line) onto each data of (dots kinematic with variables. error bars) The shadowed signal histogram MC weighted is estimated by PWA background. solution (line), assuming that signal is composed of S-wave K (89). The shadowed histogram is estimated background. To test applicability of LASS parameterization for S-wave phase, we measure phase variation of S-wave in a model-independent way. We divide m Kπ spectrum into twelve bins Inperform above PWA fitprocess to measure δ S δdepends S in eachon bin m( Kπ phase according is assumed to tolass be constant parameterization. bin). FigureThen shows we measure comparison δ S inof a model-independent model-independent way. measurement We divide with m results Kπ within each spectrum into twelve bins perform PWA fit with δ S in each bin as twelve based on LASS parameterization. We find good agreement between both determinations of additional fit parameters (within each bin phase is assumed to be constant). Figure illustrates comparison of model-independent measurement with that S-wave s phase variation. based on LASS parameterization. 14 Eq. In PWA, helicity basis form factors are assumed to depend on q () over three angles, we obta LASS para. according 1 to spectroscopic pole dominance (SPD) model. In order to achieve a better understing of semileptonic decay dynamics, we also measure formdqfactors dm = 1 G F V cs { Model Ind. dγ 1 in (4π) a 5 m βp Kπ[ F11 D 8 model-independent way using projective weighting technique, which is introduced 6 in Ref. [6]. Assuming that K (89) Only cidates in K has an infini 4 (89) region ([.8,1] GeV/c ) are used, single so that pole mass we of MeV/c 1, a can neglect or components than K (89) non-resonantqs-wave., we findthe decay intensity of D + K π + e.7 + ν e can be parameterized by form factors describing decay into vector meson K (89) m : H + (q ), m), H (q, m), H (q Kπ (GeV/c Γ, m), = B(D+ K (89) e + ν e )B( K by an additional form factor h (q τ D +, m) describing non-resonant S-wave contribution. The form factors Fig. are measured 4: The S-wave by weighting phase variation q versus distributions m Kπ assuming based on = angular. G F V cs Figure : The S-wave phase variation versus m that signal is composed of S-wave K (89) 96π. The A 1() Kπ. The points with error bars are model-independent measurements, solid line ( dotted line shows one sigma deviation from central line) is q I, points with error bars correspond to model-independent max PWA p Kπ q solution based on LASSmeasurement parameterization. I = by fitting data; solid line corresponds to result based on LASS parameterization: a 1/ B,SG =1.94, A 1 () m [ H + H D In K (89) bregion, 1/ B,SG =-.81; decay intensity dotted line of D corresponds + K π to + e one-sigma + ν e can be parameterized by three helicity basis form deviation. factors: H + (q,m), H (q,m) H (q,m), describing Here decay is into reduced Planck consta vector meson K (89), by an additional form factor h lifetime of D + (q,m) describing4 non-resonant meson. S- Using valu.7) s V cs =.986 ±. wave contribution. We extract helicity basis form factors in a model-independent way using 6 gets A 1 () =.585 ±.11 ±.17. projective weighting 1 technique sults are summarized [], The results in arethird shown infourth Fig.. columns We find of model-independent Table II. The contribution from K (141) 7 We have also calculated A is found 1 () tak measurements are consistent with SPD model with our PWA solution. Our measurements 8 tion mass are distribution of to be consistent with zero eir fixing δ K (141) at zero K (89 also consistent with CLEO-c results or π, while K [4]. decay rate over q m, we (14) 9 4 has a significance of 4.σ, fa-.586 ±.1 ± voring δ K (14) at zero. The upper limits at 9% con- 1 6 fidence level (C.L.) are calculated using a Bayesian ap- The systematic uncertainty of eac 7 proach taking into account systematic uncertainties. fined as difference between fit 8 The branching fractions upper limits are meainal condition that obtained afte 4 9 sured to be: varied corresponding to one source o 5 tematic uncertainties of PWA no 6 summarized in Table III. Uncertaint 7 fraction is estimated by varying back B(D + K (141) e + 8 ν e ) = ( ±.9 ±.8)%, one stard deviation. Uncertainties

4 posed of S-wave K (89). Model-independent measurement (points with error bars) is compared with result based on LASS parameterization (solid line, 1σ deviation is marked by dashed line). Charmed hadron The results decays at arebesiii shown in Figure. They are consistent with SPDLiaoyuan model with Dong parameters obtained from PWA, with results reported by CLEO-c [7]. Figure : Form Figure factors : Form measured factors in a model-independent measured in thisway work (squares) (squares) compared compared with with CLEO-c results CLEO- with results PWA (circles) solution based withon SPDPWA model solution (curves). (curves). Error bars represent both (circles) c statistical systematic uncertainties.. A D )(q + ) form ωe + νfactors, e D + where φe q + νis e (preliminary) invariant mass square of e + ν e system. A precise measurement of branching ratio form factors provide opportunities to test The decay stard D + ωe model + ν e has been observed oretical at CLEO-c calculations. experiment [5]. Neglecting lepton mass, The transition decay D + rate for φe D + + ν e has ωe + not ν e decays been observed depends on atthree present. dominant Theform φ (ss) factors: has different two axial quark one vector, composition A 1, A from V. The decay D meson D + (cd), φe + ν so e has not process been observed can only [6]. Its proceed rate relative eir to through D + The decay D + ωe + ν e has similar dynamics as D + K (89) e + ν e. Neglecting s ωe + ω φ mixing or non-perturbative weak annihilation (WA). A measurement ν e will provide information about ω φ mixing, as well as about non-perturbative of branching mass fraction of electron, can discriminate transition which matrix process element is dominant. of D to vector meson can weak annihilation. The be signal decomposed yields are into determined contributions by from variable one vector U, V (q ) difference two axial-vector between (A 1, With double-tag technique, U miss distributions with all tag modes combined for D + missing ωe + energy ν e D + φe + momentum [8]. The yield of D + ωe + ν e are shown in Fig. 4. For decay D + ν e is ωe + obtained from a fit ν e, signal yield is to U distribution as shown in left plot of Figure 4. And that of D + φe + ν obtained from fit to U miss distribution. For decay D + φe + e is obtained by counting number in signal region [-.5, ν e, we.7] observed GeV as events shown in in signal right region plot, ([-.5, indicating.7] GeV) nowith significant 4. ± 1.5excess background. of signal The events. absolute branching The results fraction are of concluded decay D in + Table ωe + 1, ν e which are upper improved limit oncompared B(D + with φe + previous ν e ) at 9% reports. C.L. are listed in Table 1. These results are most precise measurements to date. Measurement of form factors in decay D + ωe + ν e search for decay D + φe + ν e /1MeV Umiss (GeV) /1MeV Umiss (GeV) Figure 4: 4: Left: Left: fit to fit U(solid miss distribution line) to for D + U distribution ωe + ν e. Right: indata U miss (points distribution with for D error + φe bars) + ν e. The forpoints D + with ωe error + ν e bars. The aretotal data. Inbackground left plot, solid is shown line is byfit, filled curve, is with total background, peaking component cross-hatched showncurve by is cross-hatched peaking background. curve. In right Right: plot, solid U distribution histogram for signal D + MC with φe + arbitrary ν e in data normalization, (points with error arrows bars) show signal signal region. MC with arbitrary normalization (solid histograms). The arrows show signal region. We perform a five-dimensional maximum likelihood fit in space of m (mass square of πππ, q, cosθ 1 (helicity angle of ω), cosθ (helicity angle of e) χ (angle between decay plans), to measure form factors in decay D + ωe + ν e. The form factor ratios are deter- Table 1: Measured branching fractions a comparison with previous measurements. For D + ωe + ν e, first uncertainty 4 is statistical second systematic. Mode This work Previous [8, 9] ωe + ν e (1.6 ±.11 ±.8) 1 (1.8 ±.18 ±.7) 1 φe + ν e (9%C.L.) (9%C.L.)

5 Liaoyuan Dong Table 1: Measured branching fractions a comparison with previous measurements. For B(D + ωe + ν e ), first uncertainty is statistical second systematic. Mode Measured B Previous [5, 6] ωe + ν e (1.6 ±.11 ±.8) 1 (1.8 ±.18 ±.7) 1 φe + ν e (9%C.L.) (9%C.L.) Sec.. The form factor ratios are determined from fit: r V = 1.4 ±.9 ±.6, mined r from fit: r V = V () A 1 () = 1.4 ±.9 ±.6, r = A () = 1.6 ±.15 ±.5, which are measured for first A 1 time () = 1.6 in± this.15 decay. ±.5, The which fitted are measured projections for over firs time. fiveprojections variablesof are illustrated five kinematic Figure variables5. are shown in Fig (a) m (GeV /c ) (d) cosθ 16 (b) q (GeV /c ) (e) 1 1 χ 1 (c) cosθ 1 Figure 5: 5: Projections of data of (points data withset error (points bars), with of error fit (solid bars), histograms) fit results onto each(solid of kinematic histograms) variables. The filled sumhistogram of curves background show background distributions distributions. (filled histogram curves) onto (a) m, (b) q, (c) cosθ 1, (d) cosθ (e) χ. 4. D + K L e+ ν e (preliminary) We present first measurement of absolute branching fraction CP violation for 4 Study of decay dynamics CP asymmetry in decay D + D + KL K e+ Le ν e. + With double-tag technique, we measure branching fractions of six tag modes separatelyν for e decay D + D. We obtain B(D + KL e+ ν e ) = (4.454 ±.8 ±.1)%, B(D KL In charged D meson e ν e ) = (4.57 ±.8 ±.14)%, which are weighted averages of six tag modes. We obtaindecays, averaged CP branching asymmetry fraction occurs B(D when + K absolute value of L decay amplitude for D decaying to a final state is different e+ ν e ) = (4.481 ±.7 ±.1)%, which agrees well with measurement of B(D + K from one for S corresponding CP -conjugated amplitude. The most optimistic e+ ν e ) by CLEO-c [7]. We also model-dependent estimates put SM predictions CP B(D+ KL e+ ν e ) B(D KL e ν e ) obtain CP asymmetry A = (.59±.6±1.48)%, for asymmetry as O(1 which is B(D + KL e+ ν e )+B(D KL e ν e ) ) or below [1], so an consistent with oretical prediction in Ref. [8]. observation of any CP -violating signal would be a sign of new physics. The hadronic matrix In element limit of zero of D electron to pseudoscalar mass, differential meson process decay rate can for be D decomposed + KL e+ ν e depends into contributions one form fromfactor longitudinal f + (q ). We perform transverse simultaneous form factors. fits Neglecting distributions oflepton observed mass, only on cidates only as transverse a functionform of q factor for sixcontributes. tag modes to Various determined oretical f+ K () V techniques cs. We useprovide several parameterizations slightly different forq dependencies f + (q ): simple of pole form model, factors, modified High precision pole model, measurements two-parameter series of expansion, partial decay three-parameter width over different series expansion. rangesfigure of q 7will shows distinguish simultaneous which fits method using correctly two-parameter describes series expansion non-perturbative model, corresponding dynamics oftoqcd. results: The D + f+ K () V KLe + cs = ν e.78 decay ±.6 is investigated ±.11, inshape thisparameter work with r 1 its = 1.91 branching ±. fraction ±.4. CP violation firstly measured. q dependence of form factors are measured based on different oretical models for first time as well. 5 5

6 cidates as a function of q to determined product of hadronic form factor CKM matrix element f+ K () V cs. The form-factor shape is described based on simple pole model (m pole ), modified pole model (α), two-parameter series expansion (r 1 ), three-parameter series expansion (r 1, r ). As an example, Figure 7 shows Charmed hadron simultaneous decays at BESIII fits using two-parameter series expansion model, Liaoyuan corresponding to results: f+ K () V cs =.78 ±.6 ±.11, r 1 = 1.91 ±. ± Dong.4. Figure 6: Fits (blue solid curves) to observed cidates (points with error bars) as a function of q Figure 7: (Color online) Simultaneous fits (blue solid curves) to numbers by of two-parameter D + KLe + series expansion parameterization. In each plot, red dashed ν e data (points with error bars) as a function of q curves show signal, while with two-parameter yellow, violet, black green curves refer to different kinds of backgrounds. series expansion parameterization. The red dashed curves show signal, while violet, yellow, green black curves refer to different kinds of backgrounds. 5. Λ + c Hadronic decays (preliminary) Hadronic Λ + c decays rates are key probes to underst b-flavor meson baryon decays. Experimentally, most of branching fractions of Λ + c are measured referring to pk π + mode. 5However, Summary PDG has made a model-dependent determination of absolute B(Λ + c pk π + ) = (5. ± 1.)% with large uncertainty [9]. Recently, Belle reports a model-independent measurement Based of B(Λ on +.9 fb 1 of data collected by BESIII experiment three semileptonic c pk π + ) = (6.84 ± )%, which improve precision by a factor of 5. decays Using are analysed. double-tagin technique, study we measure of D + absolute K π + e + branching ν e, its branching fractions forfractions twelve Cabbibofavored hadronic B(D + Λ + K π + e + ν e ) = (.71±.±.8)%, B(D + K π + e + ν e ) [.8,1] = are measured: c decay modes. The ST DT yields are obtained by fitting M BC distributions ±. of ±.7)%. Λ c cidates. A PWAWe isperform performed a least square S-wave fit, which contribution considers statistical is found to (. account systematic for correlations (6.5±.±.18)%. among different The hadronic S-wave modes, phase to obtain form branching factors fractions are measured of both twelve by Λ + PWA in a model-independent way, showing good consistency. For c decay decay D + modes ωe + globally. Table lists resultant ST yields DT yields, as well as ν e, branching fraction is measured with a higher precision: fitted B(D + branching ωe + fractions of Λ + c, where uncertainties are statistical only. Our result on ν e ) = (1.6 ±.11 ±.8)%. Its form factors are determined for first B(Λ + c pk π + ) is consistent with that in PDG, but lower than Belle s with a time: r V = 1.4 ±.9 ±.6, r = 1.6 ±.15 ±.5. The rare decay D + significance φe + of ν e is about σ. For branching fractions of or modes, precisions of our measurement are significantly improved comparing to world average values in PDG Λ + c Λe + ν e (preliminary) The Λ + c Λe + ν e decay provide a good test on non-perturbation oretical models calibrate calculations of lattice quantum chromodynamics (LQCD) in charm baryon sector. Using similar strategy in Section 5, we obtain signal yield by fitting U miss distribution for cidate events, as shown in Fig. 7. We obtain number of signals to be 1.5 ± 1.9 after subtracting number of background. The absolute branching fraction for Λ + c Λe + ν e is determined to be B(Λ + c Λe + ν e ) = (.6±.8)%, where error is statistical only. Our result improves precision of PDG value more than twofold. 6

7 Liaoyuan Dong / Nuclear Particle Physics Proceedings (15) 1 4 Table : ST yields, DT yields, pπ ) [], we measured get B(Λ branching + c Λe + ν e fractions ) = (.6 with ±.8)%, comparisonprecisions to PDG values in this work are improved by facto Belle measurement. For our results, where rror uncertainties is statisticalare only. statistical only. The branching comparing fractions to do not world average values in include any sub decay rates. also report first model-independent me t of absolute branching fraction B(Λ + c Mode ST yield DT yield Measured B (%) PDG B (%) Belle (.6 B(%) ±.8)%. [1] This work improves prec pks 14 ± 7 89 ± ± ±. than twofold, thus providing a stringent test pk π + 68 ± 88 9 ± ±.7 5. ± ± oretical models. pks 4 π 558 ± 4 ± ± ±.5 pks π+ π 454 ± 8 9 ± ±.1 1. ±.5 Acknowledgements pk π + π 1849 ± ± ±..4 ± 1. Λπ + The BESIII Collaboration thanks staff 76 ± 7 59 ± 8 1. ± ±.8 Λπ + π computing center for ir strong sup 1497 ± 5 89 ± ±.5.6 ± 1. Λπ + π π + 69 ± 1 5 ± 7.67 ±..6 ±.7 Σ π + References 586 ± 9 ± ± ±.8 /.1 GeV/c Σ + π 71 ± 5 ± 5 M1.18 pπ (GeV/c ±.11 ) 1. ±.4 Σ + π + π 86 ± 4 Figure 56: ± M8 pπ distribution.58 ± for. Λ +.6 ± 1. Σ + c Λe + ν e cidates. ω 157 ± 1 ± 1.47 ±.18.7 ± 1. /.1 GeV U miss (GeV) Figure 4: Fit to U miss distribution within Λ signal region. The (red) solid line shows total fit (blue) dashed line is background shape. Figure 7: Fit to U miss distribution for Λ + c Λe + ν e. The points with error bars are data, (blue) solid line shows total fit (red) dashed line is background shape. References 4. Summary [1] R. M. Baltrusaitis et al. (MARK III Collaboration), Phys. Rev. Lett. 56, 14 (1986). To summarize, twelve Cabibbo-favored Λ + c decay [] N. Cabibbo A. Maksymowicz, rates are measured Phys. Rev. by employing B 17, 48 a DT technique, based on a sample of threshold data at (1965). s = GeV collected at BESIII. This is first absolute measurements [] J. M. Link et al. (FOCUS Collaboration), Phys. Lett. B 6, 18 (6). [4] R. A. Briere et al. (CLEOofCollaboration), Λ + c decay branching Phys. Rev. fractions D 81, 111 at Λ (1). + c Λ c production threshold, after Λ + c was discovered years a- [5] S. Dobbs et al. (CLEO Collaboration), go. Their comparisons Phys. Rev. with Lett. previous 1, 118 results from (1). [6] J. Yelton et al. (CLEO Collaboration), PDG Belle Phys. are presented Rev. D in 84, TABLE 1. (11). For golden mode B(pK π + ), our result is consistent with that in [7] D. Besson et al. (CLEO Collaboration), PDG, but lower than Phys. Belle s Rev. with D 8, a significance 5 (9). of about σ. For branching fractions of or modes, [8] Z. Z. Xing, Phys. Lett. B 5, 1 (1995); Phys. Lett. B 6, 66 (1995). [9] K. A. Olive et al. (Particle Data Group), Chin. Phys. C 8, 91 (14). [1] A. Zupanc et al. (Belle Collaboration), Phys. Rev. Lett. 11, 4 (14). [1] G. S. Abrams, M. S. Alam, C. A. Blocker, A. Boya denbach, D. L. Burke, W. C. Carirs W. Chi Phys. Rev. Lett. 44 (198) 1. [] K.A. Olive et al. [Particle Data Group], Chin. 91 (14). [] A. Zupanc et al. [Belle Collaboration], Phys. R 4 (14). [4] R. Pérez-Marcial et al., Phys. Rev. D 4, 955 (19 [5] M. Avila-Aoki et al., Phys. Rev. D 4, 944 (1989 [6] F. Hussain et al., Z. Phys. C 51, 67 (1991). [7] G. V. Efimov et al., Z. Phys. C 5, 149 (1991). [8] Robert Singleton, Phys. Rev. D 4, 99 (1991). [9] A. Garcia R. Huerta, Phys. Rev. D 45, 66 (1 [1] H. Y. Cheng B. Tseng, Phys. Rev. D 5, 1457 [11] H. G. Dosch et al., Phys. Lett. B 41, 17 (1998). [1] R. S. Marques de Carvalho et al., Phys. Rev. D (1999). [1] M. Pervin et al., Phys. Rev. C 7, 51 (5). [14] Y. L. Liu et al., Phys. Rev. D 8, 7411 (9). [15] R.M.Baltrusaitis et al. [MARK-III Collaboration Lett. 56, 14 (1986); J.Adler et al. [MARK-III C Phys. Rev. Lett. 6, 89 (1988). [16] H.Albrecht et al. [ARGUS Collaboration], Phys 41, 78 (199). [17] Y. Guan, X. R. Lu, Y. Zheng Y. S. Zhu, Chin 161 (1). [18] J. Y. GE et al. [CLEO Collaboration], Phys. Rev. (9). 7