Recent results from BESIII

Transcription

1 Recent results from BESIII Yangheng Zheng On behalf of BESIII Collaboration University of Chinese Academy of Sciences Nov. 6, 2015 EINN 2015, Paphos, Cyprus

2 Other BESIII presentations Stefano Spataro: Spectroscopy in the charm region: from BESIII to Panda Zhiqing LIU: XYZ states: BESIII Results Martin Ripka: pion form factor measurement at BESIII Martin Ripka: An Improved Limit for Gamma_ee of X(3872) and Gamma_ee Measurement of psi(3686) [poster] Samer Ahmed: Analysis of e+e nn from 2015 Scan Data at BESIII [poster] 2

3 Outline Introduction to BEPCII/BESIII Selected recent results XYZ & Charmonium decays Form Factors & Fragmentation Functions Light Hadron Spectroscopy Charm hadron decays Summary 3

4 Beijing Electron Positron Collider (BEPC) beam energy: GeV LINAC e+ BESIII detector 4 e- 2004: started BEPCII upgrade, BESIII construction 2008: test run now: BESIII physics run (BEPC): Lpeak=1.0x1031 /cm2s 2009-now (BEPCII): Lpeak=0.85x1033/cm2s

5 BEPCII Top-up injection Continuous beam injection realized during Synchron Radiation period (electron injection) in July, 2015 Plan: apply to electron-positron collision mode in coming run period (December) Ldt increasing ~30% 5

6 BESIII Detector MDC NIM A614, 345 (2010) CsI(Tl) EMC R inner: 63mm ; R outer: 810mm Length: 2582 mm Layers: 43 Crystals: 28 cm(15 X 0 ) Barrel: cos <0.83 Endcap: 0.85 < cos < 0.93 RPC MUC TOF BTOF: two layers ETOF: 48 for each 6 BMUC: 9 layers 72 modules EMUC: 8 layers 64 modules

7 BESIII data samples J/ 1.3x x fb fb fb -1 (3770) 2.9 fb fb fb fb -1 ~130 points for R Scan (~1.3 fb -1 ) World largest J/, (2S), (3770), Y(4260), produced directly from e + e - collision 7

8 BESIII Collaboration US (5) Univ. of Hawaii Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana Europe (13) Germany: Univ. of Bochum, Univ. of Giessen, GSI Mongolia (1) Univ. of Johannes Gutenberg Institute of phys. & Tech. Helmholtz Ins. In Mainz Russia: JINR Dubna; BINP Novosibirsk Korea (1) Italy: Univ. of Torino,Frascati Lab, Ferrara Univ. Netherland:KVI/Univ. of Groningen Seoul Nat. Univ. Sweden: Uppsala Univ. Turkey: Turkey Accelerator Center Pakistan (2) Univ. of Punjab COMSAT CIIT ~400 members from 55 institutions in 12 countries 8 China(32) IHEP, CCAST, UCAS, Shandong Univ., Univ. of Sci. and Tech. of China Zhejiang Univ., Huangshan Coll. Huazhong Normal Univ., Wuhan Univ. Zhengzhou Univ., Henan Normal Univ. Peking Univ., Tsinghua Univ., Zhongshan Univ.,Nankai Univ., Beihang Univ. Shanxi Univ., Sichuan Univ., Univ. of South China Hunan Univ., Liaoning Univ. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Suzhou Univ., Hangzhou Normal Univ. Lanzhou Univ., Henan Sci. and Tech. Univ. Univ. of Sci. & Tech. Liaoning Japan (1) Tokyo Univ.

9 Physics Topics at BESIII Hadron spectroscopy search for the new forms of hadrons meson spectroscopy baryon spectroscopy Study of the production and decay mechanisms of charmonium states: J/, (2S), C (1S), C{0,1,2}, C (2S), h C ( 1 P 1 ), (3770), etc. Calibrate QCD XYZ states Int. J. Mod. Phys. A, Vol. 24 (2009) Precision measurement of R values, hadron FF,... Charm physics Charm hadron decays Rare decays, new physics 9

10 XYZ & Charmonium decays Please also see Zhiqing Liu s talk XYZ states: BESIII Results and Stefano Spataro s talk Spectroscopy in the charm region: from BESIII to Panda

11 Charmonium(-Like) spectroscopy from Ryan Mitchell Charmonium states below open charm threshold are all observed Above open charm threshold: 11 many expected states not observed many unexpected observed Z(4430) Z(4250) Z(4050) Z(3900) X(3872) XYZ(3940) X(3915) X(4160) Y(4008) Y(4140) Y(4260) Y(4360) X(4350) Y(4660)

12 The Z c family at BESIII Zc(3900) +? Zc(3900) 0? Zc(4020) +? Zc(4020) 0? Zc(3885) +? Zc(3885) 0? Zc(4025) +? Zc(4025) 0? States observed via open charm decays and via pion decay have compatible mass and width we are seeing two isospin triplets in two different decay modes PWA shows: Zc(3900) J P = e + e π 0 (D D ) 0 e + e π 0 (D D ) 0

13 Search for Z c (3900) ± light hadrons No significant Z c ω π Phys. Rev. D92, V 13 e ] + e π ± Z c (3900), Z c (3900) ωπ] < 0.26 GeV e ] + e π ± Z c (3900), Z c (3900) ωπ] < 0.18 GeV Br(Z c (3900) ωπ) < 0.2% (Γ ωπ < 70 C.L. It may indicate that the annihilation of c c in Z c (3900) ± is suppressed.

14 What are these Z c states? Tetraquark Compact object formed from (Qq) and (Qq) Hadro-Quarkonium Compact (QQ) surrounded by light quarks Hadronic-Molecule Extended object made of (Qq) and (Qq).or mixtures of such configurations with/without conventional charmonium states The structure is not well understood; the charged structures must contain at least two quark/antiquark pairs. 14

15 Other Charmonium transitions Observation of X(3823) in e + e - p + p - X(3823) p + p - g c1 Phys. Rev. Lett. 115, (2015) Good candidate of (1 3 D 2 ) Observation of e + e - c0 (Phys. Rev. Lett. 114, ) Inconsist with Y(4260) from ππj/ψ No significant signals for e+e ωχ c1,2 Observation of e + e - J/ (Phys. Rev. D91, (2015)) Agree with previous results with improved precision non-trivial structure around 4.2 GeV Searches for c0,2 p 0 c (Phys. Rev. D91, (2015)) Isospin violating transitions No significant η c signals are observed, and upper limits are set. Branch fraction measurement contradicts to QCD multipoleexpansion (PRD 75, ) prediction.

16 Form Factors & Fragmentation Functions Please also see Martin Ripka s talk for pion form factor measurement at BESIII.

17 Time-Like Baryon Form Factors en en, Λ Λ Space-like: FF real Time-like: FF complex Fundamental properties of the baryon QCD predictions: at large q 2, absolute value of FF(q 2 )=FF(-q 2 ) Experiment: time-like FF much larger than space-like FF Squared ratio of n/p form factors 0.25 Problem: only very poor data for neutron form factor 17

18 Proton Form Factors from 2012 run Phys.Rev. D91 (2015) 11, Analysis Features: Production rate Form factor Polar angle distribution GE/GM Radiative corrections from Phokhara8.0 (scan) Normalization to e + e - e + e -, e + e - γγ (BABAYAGA 3.5) G E /G M ratio obtained for 3 c.m. energies E cm /GeVA L int / pb A , 3.06, , 3.50, 3.54, , 3.65,

19 New scan in GeV ; From high to low; 20 energy points, total online luminosity 525 pb -1 ; Added 2.05 GeV; Allows for form factor measurements, threshold studies, 19 6-month plan, finished in 4 months.

20 Proton FF: expectation from 2015 data Based on the new scan data in GeV: 15% 15% δ R EM / R EM ~ 9% - 35% δ G M / G M ~ 3% - 9% δ G E / G E ~ 9% - 35% 20 Will top BaBar result First time extraction without any assumption! Neutron, FF: analysis on going

21 Collins Fragmentation Function(FF) J. C. Collins, Nucl.Phys. B396, 161 (1993) D. Boer Nucl.Phys.B806:23(2009): e + e q q π 1 ± π 2 X P. Sun, F. Yuan, PRD (2013) arxiv Predicted Collins asymmetries for BESIII : Collins FF describes the behavior of hadron produced from a transversely polarized quark depends on leads to an azimuthal modulation of hadrons around the quark momentum Experimentally Double Ratio to cancel detection effects Unlike-sign ; Like-sign: Charged: 21

22 Collins effect at BESIII First time measurement in Low Q 2 13GeV 2 at e+e- collision vs. z 1,z 2 arxiv Submitted to PRL denote asymmetries for UL and UC ratios, respectively 22 vs. p t ~62 pb Continuum region Nonzero Collins effect at BESIII Basically consistent with predictions from PRD (2013). important inputs for understanding the spin structure of the nucleon valuable to explore the energy evolution of the spin-dependent fragmentation function.

23 Light Hadron Spectroscopy

24 Light glueballs and hybrids Charmonium decays provide ideal hunting ground Gluon-rich process Clean high statistics data samples from e+eannihilation I(J PC ) filter in strong decays of charmonium Odd-balls in LQCD 24

25 X(1835) in J/ g K 0 SK 0 S Phys.Rev.Lett (2015) Observation and Spin-Parity Determination The structure around 1.85 GeV/c 2 in the K S K S η mass spectrum is strongly correlated to f 0 (980) Partial Wave Analysis for M(K S K S )<1.1 GeV/c 2 X(1835) K S K S η (the K S K S system is dominantly produced through the f 0 (980)) J PC =0 -+, (> 12.9 σ) M=1844±9(stat) 25(syst) MeV/c2, Γ= MeV, Consistent with X(1835) observed in J/ψ γπ + π η B(J/ψ γx(1835)*b(x(1835) K s K s η)=( )*10-5 X(1560) f 0 (980)η: J PC =0 -+, (> 8.9 σ) M=1565±8 63 MeV/c2, Γ= MeV consistent with those of η(1405) / η(1475) within 2.0 σ

26 Model-independent PWA of J/ gp 0 p 0 Phys. Rev. D 92, (2015) A sophisticated mass independent amplitude analysis is performed. Significant features of the scalar spectrum include structures near 1.5, 1.7, and 2.1 GeV/c 2 26

27 Partial Wave Analysis of J/ψ γφφ (preliminary) Besides η(2225), very little was known in the sector of pseudoscalar above 2 GeV. The new experimental results are helpful for mapping out the pseudoscalar excitations and searching for 0 -+ glueball Dominant contribution from pseudoscalars η(2225) is confirmed; two additional pseudoscalars η(2100) and X(2500) are observed. The three tensors f 2 (2010), f 2 (2300) and f 2 (2340) stated in p - p reactions are also observed with a strong production of f 2 (2340). 27

28 Glueballs from Quenched LQCD Low lying glueballs have ordinary quantum number mixing with qqbar mesons Phys. Rev. D 73, Phys. Rev. Lett. 110, Phys. Rev. Lett. 111, At BESIII f 0 (1710) and f 0 (2100) are observed with a strong production in J/ψ γ ηη [PRD87, ] (as well as MIPWA of J/ψ γπ 0 π 0 ) f 2 (2340) is observed with a strong production in J/ψ γηη/φφ (as well as MIPWA of J/ψ γπ 0 π 0 ) Systematic studies ongoing J/ψ γηη J/ψ γη η J/ψ γk s K s J/ψ φx, ωx

29 Observation of the Dalitz decay ge + e - Phys.Rev.D 92,012001(2015) Measured for the first time Contains information about time-like FF at small q2 At large q2, strong enhancement compare to QED calculation for pointlike hadron Possible explanation: vector meson dominance model (VMD) 29

30 Light Baryon Spectroscopy JLAB, MAMI, ELSA,.. Charmonium decays provide novel insights into baryons and complementary to other experiments Isospin 1/2 filter: ψ N Nπ, ψ N Nππ Missing N* with small couplings to πn & γn, but large coupling to gggn : ψ N Nπ/η/η /ω/φ, pσπ, pλk Not only N*, but also Λ, Σ, Ξ Gluon-rich: a favorable place for hybrid (qqqg) baryons Interference between N* and N * bands in ψ N Nπ Dalitz plots may help to distinguish some ambiguities in PWA of πn High statistics of BES III 30

31 Study of N* and * 31 2 New N* are found (1/2+, 5/2-)

32 Charm Hadron Decays Threshold production at 3.773, 4.03, 4.17 GeV, 4.6GeV e + e D D, D s + D s, D s D s, Λ c + Λ c

33 Precision measurement of CKM elements CKM matrix elements are fundamental SM parameters that describe the mixing of quark fields due to weak interaction. d s' ' b' 5% precision 10% precision V V V ud cd td V V V us cs ts V V V Three generations of quark? Expected precision < 2% at BESIII cb tb ub d s b Unitary matrix? -- a precise test of SM model New physics beyond SM? BESIII + B factories + LQCD BESIII + B factories + LHCb + LQCD 33

34 Form Factors: Semileptonic decays dg( D K ( p )en ) dq 2 = G F V cs( d) PK ( p ) f 24p 3 + q 2 ( ) 2 D (s) P l (Theoretically clean) Measure V cx x FF Charm physics: CKM-unitarity V cx, extract FF, test LQCD Input LQCD FF to test CKM-unitarity B physics: Validate LQCD for form factor, extract V ub to test CKM-unitarity Example: B p l V ub = (Theory) x 10-3 on LQCD Form Factor calculations (provide perfect 34 calibration) q 2 =(p l +p ) 2 M 2 inv of lepton pair

35 Form Factors: D 0 K(p) e + PRD 89, (R) (2014) Signal side reconstruction: Tag plus exactly two oppositelycharged tracks Kaon/pion/electron ID Electron has right charge No extra neutral energy 35 U = E miss - P miss» 0 Kinematic variable: U miss

36 Form Factors: D 0 K(p) e + PRD 89, (R) (2014) 36 BESIII: the most precise measurements The error of f + D p is still dominated by statistics.

37 Λ c + : cornerstone of charmed baryon spectroscopy Quark model picture: a heavy quark (c) with a unexcited spin-zero diquark (u-d) Heavy Quark Effective Theory: more reliable prediction of heavy-light quark transition without dealing with light degrees of freedom that have net spin or isospin. Λ c + provides more powerful test than D/Ds does 37

38 Charm baryon c decays BESIII: c Pair production at threshold (4.6GeV) Largest data GeV Double Tag Model-independent absolute c decay Branching fractions ST Λ c ± yields Belle: first model-independent Measurement (PRL113,042002) DT Λ c ± yields 38 Preliminary results: statistical error only!

39 Events /0.010 (GeV) Absolute BR for c + e + e Dominated process: c + e + e Input for LQCD calculations First absolute BF measurement & Form Factors Theoretical predictions: 1.4% ~ 9.2% arxiv: submitted to PRL subtraction of backgrounds: ± 10.9 signal yields: ± 10.9 U miss (GeV) + + BESIII Prel. : B( e ) ( )% c e non-st events: negligible sidebands: 1.4±0.8 μ + + π + π 0 + π + =4.5± Statistical limited measurement! Best precision to date

40 Prospects for c decays Can BEPCII challenge the CM energy limit at 4.6 GeV? With larger c data sample PWA intermediate structures in 3-body decays More semileptonic decays: nl, *l, Xl Decay asymmetry parameters c + BP/BV c + Rare decays search Weak radiative decay c+ g + FCNC c+ pl + l - LNV c+ pe 40 Current How 4.63Gev?

41 BESIII upgrade Main Drift Chamber: Malter effect found in inner chamber in 2012, add water vapor to the chamber to cure the aging problem. A new inner drift chamber has been built at IHEP this summer. Cylindrical-GEM (CGEM) as the inner chamber ongoing : Italy group in collaboration with groups in Germany, Sweden and IHEP. New Endcap TOF (built by USTC & IHEP) system was installed this summer to improve the time resolution (100ps ~55ps) 41

42 Outlook (data taking plan) Previous data BESIII present & future Goal J/ BESII 58M 1.2 B 20* BESII 10 B CLEO:28 M 0.5 B 20* CLEOc 3B CLEO:0.8/fb 2.9/fb 3.5*CLEOc 20 /fb Above open charm threshold (4160) (4040) 2.3/fb@~4260, 0.5/fb@ /fb@4600,1/fb@ /fb R scan & Tau BESII GeV at 105 energy points GeV at 20 energy points Y(2175) 100 pb -1 (4170) 42 3 fb -1 ( next run)

43 Summary and prospect Rich Physics Program at BESIII In 2015, 35 paper published or submitted (9 PRL) Many new results have been released recently. More Charmonium(-like) resonances observed New resonances in light hadron spectroscopy important parameters & constants: precision measurement of FF and decay constants, not covered today: R scan, tau lepton mass, searching for BSM physics BESIII will be running for another 5-7 years, with an upgraded detector configuration: expect to see a lot of exciting results in the future! 43

44 44 Thank you!

45 Backup slides

46 Charm facilities Hadron colliders (huge cross-section, energy boost) Tevetron (CDF, D0) LHC (LHCb, CMS, ATLAS) e + e - Colliders (more kinematic constrains, clean environment, ~100% trigger efficiency) B-factories (Belle, BaBar) Threshold production (CLEOc, BESIII) Only Charm hadron pairs, no extra CM Energy for pions Quantum Correlations (QC) and CP-tagging are unique Lots of systematic uncertainties cancellation while applying double tag technique 46

47 Energy regime 47

48 Y(2175) in J/ p + p - Phys.Rev.D 91,052017(2015) 48 Confirm the existence of Y(2175) (>10 ) in f 0 (980) mass spectrum Mass and width are consistent with former results Clear f 1 (1285), (1405)/ (1440) signals Searching for X(1835) and X(1870) in pp mass spectrum