Experiments on heavy flavour spectroscopy and exotic states Liming - PowerPoint PPT Presentation

Experiments on heavy flavour spectroscopy and exotic states Liming Zhang (Tsinghua University) On behalf of the LHCb Collaboration QNP 2018 (13-17 Nov. 2018, Tsukuba, Japan)

Outline n Experimental method n X(3872) n Y(4260) # → 𝜃 & 𝜌 # state n Evidence of a 𝑎 " n Studies of doubly-charmed baryon n New results on bottom and charm spectroscopy L. Zhang 2

Introduction Since then, more than 20 non-standard hadrons that contain 𝑑𝑑̅ or PRL 91 (2003) 262001 + quarks have been found and studied, called XYZ states 𝑐𝑐 S. Olsen, arXiv:1511.01589 Charmonium spectroscopy Above open charm threshold: • many expected states not observed • many unexpected observed X(3860) Z(4430) X(3872) X(3915) Z(4050) X(4140) Z(4250) Y(4260) Z(3900) Y(4360) X(3872) discovery turned Z(4020) Y(4660) out to be the harbinger of Z(4200) ... a new direction in hadron spectroscopy L. Zhang 3

Introduction n Recent experiments show evidences for the existence of exotic hadrons + containing 𝑑𝑑̅ or 𝑐𝑐 q Numbers of charged 𝑎 - states, smoking gun for four-quark meson q Two strong candidates for pentaquark states, 𝑄 & (4380) and 𝑄 & (4450) that both decay to 𝐾/𝜔𝑞 n However many efforts needed to uncover their nature Pentaquarks Charged 𝒂 𝒅 𝟒𝟘𝟏𝟏 - < → observed in 𝛭 ; observed in 𝑍(4260) decays 𝐾/𝜔𝑞𝐿 # decays PRL110 (2013) 252001 PRL110 (2013) 252002 PRL115 (2015) 072001 PRL117 (2016) 082002 𝑸 𝒅 𝟓𝟓𝟔𝟏 - 𝑸 𝒅 𝟓𝟒𝟗𝟏 - 𝑛 ?/@A (GeV) L. Zhang 4

Experimental methods for XYZ states Modified from [HX Chen et. al. Phys. Rep. 639 (2016) 1] Υ ; (10860) 𝑑, 𝑐 𝐟𝐰𝐟𝐨 ±- or 1 ## 𝐷 = + 𝐩𝐞𝐞 ≠ 𝟐 -- 𝒀 𝟒𝟗𝟖𝟑 𝒁 𝟓𝟑𝟕𝟏 𝒂 𝒅 𝟒𝟘𝟏𝟏 -,𝟏 𝒀 𝟒𝟘𝟓𝟏 𝒀 𝟒𝟘𝟐𝟔 𝒀 𝟒𝟘𝟐𝟔 𝒁 𝟓𝟑𝟑𝟏 𝒂 𝒅 𝟓𝟏𝟑𝟏 -,𝟏 𝒀 𝟓𝟐𝟕𝟏 𝒀 𝟓𝟒𝟔𝟏 𝒀 𝟓𝟐𝟓𝟏 𝒁(𝟓𝟒𝟕𝟏) 𝒂 𝒄 𝟐𝟏𝟕𝟐𝟏 -,𝟏 𝒀(𝟒𝟗𝟕𝟏) 𝒀 𝟓𝟑𝟖𝟓 𝒁(𝟓𝟒𝟘𝟏) 𝒂 𝒄 𝟐𝟏𝟕𝟔𝟏 - 𝒀 𝟓𝟔𝟏𝟏 𝒁(𝟓𝟕𝟕𝟏) B-factories ： 𝒀 𝟓𝟖𝟏𝟏 𝒁 𝒄 (𝟐𝟏𝟗𝟕𝟏) n 𝒂 𝟓𝟓𝟒𝟏 - Main suppliers of new information about q quarkonium states for the last decade 𝒂 𝟓𝟏𝟔𝟏 - 𝒂 𝟓𝟑𝟔𝟏 - Charm- t factories ： n 𝒂 𝒅 𝟓𝟑𝟏𝟏 - Extensively studied charmonium states q 𝑸 𝒅 𝟓𝟒𝟗𝟏 - Hadron machines: n 𝑸 𝒅 𝟓𝟓𝟔𝟏 - Prompt quarkonium production in high energy q Color indicates as first observation Charmonium produced in B-decays L. Zhang q 5

X(3872) L. Zhang 6

What is the X(3872)? PRL 91 (2003) 262001 PRL 93 (2004) 072001 c < 𝐸 ∗< threshold n Mass: Very close to 𝐸 y (2S) n Width: Very narrow, < 1.2 MeV n 𝐾 ef = 1 -- X(3872) n Production 36±7 events q In 𝑞̅𝑞/𝑞𝑞 collision – rate similar to 𝑑𝑑̅ q In B decays – KX similar to 𝑑𝑑̅ , K*X smaller than 𝑑𝑑̅ PRL 93 (2004) 162002 q 𝑍 4260 → 𝛿 + 𝑌(3872) n Decay BR: open charm ~ 50%, charmonium~O(%) q Strong isospin violation decay B (𝑌 → 𝜕𝐾/𝜔) ≈ B (𝑌 → 𝜍𝐾/𝜔) q Radiative decay both to 𝐾/𝜔 and 𝜔(2𝑇) n Nature (Very likely exotic) c < 𝐸 ∗< bound state? q Mixture of 𝜓 &o (2𝑄) and 𝐸 L. Zhang 7

Observation of X(3872) → 𝝆 𝟏 𝝍 𝒅𝟐 𝝆 𝟏 𝝍 𝒅𝟏 𝝆 𝟏 𝝍 𝒅𝟐 5.2 s 𝝆 𝟏 𝝍 𝒅𝟑 The large value for R 1 l disfavors the 𝝍 𝒅𝟐 (𝟑𝑸) interpretation for X(3872) L. Zhang 8

Y(4260) L. Zhang 9

BES II R value BES, PLB 660 (2008) 315 s(t u t v →wxyz{|}) n 𝑆 = 𝜔(4040) s(t u t v →~ u ~ v ) 𝜔(3770) 𝜔(4160) 𝜔(4415) n BES measured 𝜔(4160) : 𝜔 o (2𝐸) Mass: 𝟓𝟐𝟘𝟐. 𝟕 ± 6.0 MeV Width: 72.7 ± 15.1 MeV 𝜔(4415) : 𝜔(4𝑇) Mass: 4415.2 ± 7.5 MeV Width: 73.3 ± 21.2 MeV L. Zhang 10

The Y states Y(4360) Y(4660) Y(4260)? PRD 86 (2012) 051102(R) PRD 91 (2015) 112007 L. Zhang 11

Fine structures in Y(4260) PRL 118 (2017) 092001 PRL 118 (2017) 092002 𝞽 ( 𝑓 + 𝑓 − → 𝜌 + 𝜌 − 𝑲/𝝎 ) 𝞽 ( 𝑓 + 𝑓 − → 𝜌 + 𝜌 − 𝑲/𝝎 ) 𝞽 ( 𝑓 + 𝑓 − → 𝜌 + 𝜌 − ℎ 𝑑 ) PRD 96 (2017) 032004 arXiv:1808.02847 𝞽 ( 𝑓 + 𝑓 − → 𝝆 - 𝝆 # 𝝎(𝟑𝑻) ) 𝞽 ( 𝑓 + 𝑓 − → 𝝆 - 𝑬 𝟏 𝑬 ∗# ) L. Zhang 12

Y(4220) + new Y’s from a combined fit J. L. Zhang et al., arXiv:1805.03565 Y(4220) and Y(4390) are found to be enough to describe data below 4.6 GeV Open question: Y(4220) & Y(4390) are y (4160) and y (4415) seen in hadronic final states? L. Zhang 13

# → 𝜽 𝒅 𝝆 # resonance Evidence of a 𝒂 𝐝 L. Zhang 14

𝜽 𝒅 𝝆 # resonance in 𝑪 𝟏 → 𝜽 𝒅 𝑳 - 𝝆 # # n Charmonium-like charged states 𝑎 & q Obviously exotic, since minimal four quark structure d n 𝜃 & 𝜌 # acesses 𝐾 e other than 1 - , that several 𝑎 & # confirmed to be q “natural” 𝐾 e = 0 - , 1 # and 2 - [ 𝐾 = 𝑀 , 𝑄 = −1 Œ ] S. Olsen, T. Skwarnicki, D. Zieminska, Rev. Mod. Phys. 90 (2018) 15003 L. Zhang 15

𝑪 𝟏 → 𝜽 𝒅 𝟐𝑻 𝑳 - 𝝆 # : Signal arXiv:1809.07416 n ℒ = 4.7fb #o , including Run1+Run2(2011-2016) data n 2D fit to 𝑛(𝑞𝑞̅𝐿 - 𝜌 # ) and 𝑛(𝑞𝑞̅) distribution q Fit to obtain yields of signal, NR 𝑞𝑞̅ and combinatorial backgrounds q 𝑂 ‘’“ = 1870 ± 74 𝑪 𝟏 mass 𝜽 𝒅 mass L. Zhang 16

Dalitz-plot analysis arXiv:1809.07416 n Fit includes signal + two background components n Seven 𝐿 ∗< resonances have significant contributions q Mass and width of each 𝐿 ∗< resonance are fixed, except for LASS n Good description in all variables after adding an exotic 𝑎 & component L. Zhang 17

𝑳 ∗𝟏 only fit arXiv:1809.07416 Candidates / (40 MeV) Candidates / (40 MeV) 500 160 (a) (c) LHCb LHCb 140 400 120 100 300 80 200 60 40 100 20 0 0 0.5 1 1.5 2 3 3.5 4 4.5 5 η π − π − + m ( ( 1 S) ) [GeV] m ( K ) [GeV] c Candidates / (40 MeV) 140 (e) LHCb * 0 Data Total PDF K (1680) 120 100 * * 0 0 Combinatorial bkg K (892) K (1410) 80 60 → π − * 0 + π − + 0 B p p K (NR) bkg K S-wave K (1430) 40 2 20 0 3.5 4 4.5 5 L. Zhang 18 η + m ( ( 1 S)K ) [GeV] c

𝑳 ∗𝟏 + 𝒂 𝒅 # fit arXiv:1809.07416 Candidates / (40 MeV) Candidates / (40 MeV) 500 160 (a) (c) LHCb LHCb 140 400 120 100 300 80 200 60 40 100 20 0 0 0.5 1 1.5 2 3 3.5 4 4.5 5 η π − π − + m ( ( 1 S) ) [GeV] m ( K ) [GeV] c Candidates / (40 MeV) 140 (e) LHCb * 0 Data Total PDF K (1680) 120 * * 0 0 Combinatorial bkg 100 K (892) K (1410) 80 → π * 0 − π − + + 0 B p p K (NR) bkg K S-wave K (1430) 2 60 − 40 Z (4100) c 20 0 3.5 4 4.5 5 L. Zhang 19 η + m ( ( 1 S)K ) [GeV] c

Evidence for an exotic 𝒂 𝒅 𝟓𝟐𝟏𝟏 # arXiv:1809.07416 # improve the fit −2 ln ℒ by 22.8, 41.4 and 7.0 for “natural” n Adding a 𝑎 & 𝐾 e = 0 - , 1 # and 2 - n Significance is 3.4 𝜏 after considering systematics n 𝐾 e = 1 # and 0 - are both consistent with the data -o™ MeV and Γ = 152 ± 58 #›œ -•< MeV n 𝑛 < = 4096 ± 20 #˜˜ Could it be 0 - 𝑎 4050 # → 𝜓 &o 𝜌 # from 𝐶 < decays seen by Belle? PR D85 (2008) 052003 -˜£ MeV 𝑛 < 4050 = 4051 #£< -œ< MeV Γ 4050 = 82 #˜™ -o.˜ % n Fit fraction of 𝑎 & 4100 # is 3.3 ± 1.1 #o.o ℬ 𝐶 < → 𝑎 & 4100 # 𝐿 - , 𝑎 & 4100 # → 𝜃 & (1𝑇)𝜌 # = (1.89 ± 0.64 #<.•¡ -<.¡› )×10 #œ L. Zhang 20

Doubly-charmed baryon - -- 𝛰 && 𝛰 && c c c c d u L. Zhang 21

- SELEX results on 𝜪 𝒅𝒅 & - (𝑑𝑑𝑒) reported by SELEX ! " = 1 n Observation of 𝛰 && 2 q Mass: 3518.7 ± 1.7 MeV - q Short lifetime: 𝝊 𝜪 𝒅𝒅 < 𝟒𝟒 fs @90% CL, but not zero u ×𝐂𝐆(𝜪 𝒅𝒅 u →𝜧 𝒅 u 𝑳 v 𝝆 u ) 𝝉 𝜪 𝒅𝒅 q Large production: 𝑺 = ∼ 𝟑𝟏% u ) 𝝉(𝜧 𝒅 n Not confirmed by Babar [PRD 74 (2006) 011103] , Belle [PRL 97(2006) 162001] nor LHCb [JHEP 12 (2013) 090] - → 𝒒𝑬 - 𝝆 # - → 𝜧 𝒅 𝜪 𝒅𝒅 - 𝑳 # 𝝆 - PRL 89 (2002) 112001 PLB 628 (2005) 18 𝜪 𝒅𝒅 Nsig = 15.9 6.3 s SELEX Nsig = 5.6 4.8 s SELEX L. Zhang 22

� -- from two decay modes Observation of 𝜪 𝒅𝒅 -- has n Expect 𝛰 && higher sensitivity at LHCb due to longer lifetime PRL 121 (2018) 162002 PRL 119 (2017) 112001 12 s n Observed two decay 5.9 s modes suggested by the theorists [Yu et al., arXiv:1703.09086, CPC 42 (2018) 051001] n LHCb run II at 𝑡 = 13 TeV, ~1.7 fb -1 𝑶 𝐭𝐣𝐡 = 𝟒𝟐𝟒 ± 𝟒𝟒 𝑶 𝐭𝐣𝐡 = 𝟘𝟐 ± 𝟑𝟏 L. Zhang 23