Study of ' pp at BESIII Study of pp at BESIII Xiaotao LIAO - PowerPoint PPT Presentation

Study of ψ ' → pp η at BESIII Study of ψ → pp η at BESIII — Xiaotao LIAO Institute of High Energy Physics, Beijing (On behalf of the BESIII Collaboration) XIV International Conference on Hadron Spectroscopy XIV International Conference on Hadron Spectroscopy Hadron2011, June 13~17, München, Germany

O tli Outline � Introduction to BEPCII/BESIII � Excited nucleons study at BESIII y � Study of ψ ' → pp η . St d f ' — � Summary 2

I t Introduction to BEPCII/BESIII d ti t BEPCII/BESIII Linac Linac St Storage rings i Record Luminosity : e+ ~6.49 × 10 32 cm -2 s -1 6 49 × 10 32 2 1 @ ψ (3770) BES e- 3

D t Data samples at BESIII l t BESIII � 2009 � ~106 M ψ ’ events 106 M ψ ’ events � ~225 M J/ ψ events � 2010 � ~900 pb -1 ψ (3770) events 900 pb ψ (3770) events � � 2011 � ~1800 pb -1 ψ (3770) events 1800 b 1 (3770) � ~470 pb -1 ψ (4040) events at 4.01 GeV 4

“ i i “missing” baryons problem ” b bl � Quark models predict many more baryon resonances than have been observed than have been observed � Possible explanations: � Theoretically: Reduce the number of degree of freedom. (Quark-diquark) � Experimentally: If the missing N*s have small couplings to π N & γ N, they would not have been discovered by experiments using photons or pions. 5

Ad Advantages of N* study at BESIII t f N* t d t BESIII � N* knowledge primarily from π N , γ N � At BESIII, � Pure isospin ½ P i i ½ � Study by many decay channels, such as π N, η N, ω N… — � N* and N*, twice of the statistics � Large statistics for charmonium states 6

P Previous results of BESII on N* i lt f BESII N* N*(1650) N*(1440) � Observation of N*(2050) N*(1675) N*(1520) N*(1680) ( ) N (1535) N*(1535) ? � Parameters of N*(2050) 2040 3 ± + + = 4 ± 2040 3 25 25 � M M MeV M V ψ → π − 0 / J p p Γ = ± ± 230 8 52 MeV + ⎛ 3 ⎞ : : ⎜ ⎜ ⎟ ⎟ � p J J Phys Rev D80:052004 2009 Phys.Rev.D80:052004,2009 ⎝ 2 ⎠ 7

Analysis of ψ ' → pp η (1) A l i f (1) ' — — BES-III In this analysis, only p preliminary y η→γγ are used. d A d And Br( η→γγ )=39.31% 8

Analysis of ψ ' → pp η (2) A l i f ' (2) — — 9

Introduction to P artial W ave A nalysis(PWA) � Construct amplitude A i for each possible partial wave = A A A A A A A A − i prod Breit Wigner decay � Construct differential cross section C t t diff ti l ti 2 d σ ∑ ∑ = = A A Ω i d i � Construct log likelihood function � Construct log likelihood function σ ⎛ ⎞ N d ∑ ∑ = σ ⎜ ⎟ ln ln / L ⎝ Ω Ω ⎝ ⎠ ⎠ d d = 1 i � Maximize log likelihood function g 10

PWA of ψ ' → pp η PWA f ' — — � Feynman diagrams related to ψ ' → pp η — X 11

B Best solution of PWA t l ti f PWA � N(1535) and PHSP(1/2 + ) are significant i in this analysis thi l i 12

PWA PWA projection j ti Data —MC integration background Dalitz plot of the fit result Dalitz plot data 13

M Mass and width scan of N(1535) d idth f N(1535) = Γ Γ = 2 2 1 1 . 524 524 / / 0 0 . 130 130 / / M N M N GeV GeV c c GeV GeV c c ( ( 1535 1535 ) ) ( ( 1535 1535 ) ) N N 14

S i Spin-parity(J p ) determination it (J p ) d t i ti � J P of N(1535) is ½ - , which is consistent with P f ( ) ½ the PDG value. 15

Extra 1 -- resonance scan E t 1 100MeV 200MeV 300MeV 3 5 σ 3.5 σ 600MeV 400MeV 500MeV 3 5 σ 3.5 σ 1.8 2.2 2.6 3.0 1.8 2.2 2.6 3.0 1.8 2.2 2.6 3.0 GeV/c 2 Ge /c GeV/c 2 GeV/c 2 Ge /c All the significances are less than 3.5 σ , g , and there is not likely to be a pp structure in ψ ' → pp η . — — 16

S Systematic error t ti 17

Analysis of ψ ' → pp π 0 (1) A l i f 0 (1) ' — — BES III BES-III preliminary p π 0 M 2 PWA of this channel is ongoing ongoing. Mass of pp pp M 2 p π 0 M p π ounts ? ts Co Count 18 18 Mpp(GeV/c 2 ) Mp π 0 (GeV/c 2 )

Analysis of ψ ' → pp π 0 (2) A l i f 0 (2) ' — — BES III BES-III preliminary CLEOc CLEOc CLEOc CLEOc ts Count arXiv:1007.2886v2 19 19 [hep-ex] 12 Oct 2010 Mp π 0 (GeV/c 2 )

Summary � In the PWA of ψ ′→ pp η , very significant N(1535) — component has been found. component has been found. PDG BES-III preliminary li i + + 0 . 005 0 . 010 Mass(GeV/c 2 ) 1.525~1.545 1 . 524 − − 0 . 005 0 . 004 + + 0 . 027 0 . 061 0 . 130 width(GeV/c 2 ) 0.125~0.175 − − 0 . 027 0 . 014 Br( ψ ' → pp η ) Br( ψ → pp η ) (6.6 ± 0.2 ± 0.6) × 10 -5 (6.6 ± 0.2 ± 0.6) × 10 (6 ± 1.2) × 10 -5 (6 ± 1.2) × 10 — Br( ψ ' → N(1535)p) × — ⎯ + + − × 0 . 3 7 . 4 5 5 . 5 10 − − 0 . 3 1 . 1 Br(N(1535) → p η +c c ) Br(N(1535) → p η +c.c.) � BESIII i � BESIII is a good place to study baryon resonances! d l t t d b ! 20

21 Thank you! Thank you!

B Backup k 22

B it Breit-wigner formula used in PWA i f l d i PWA 23