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

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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)

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Outline

n Experimental method n X(3872) n Y(4260) n Evidence of a 𝑎"

# → 𝜃&𝜌# state

n Studies of doubly-charmed baryon n New results on bottom and charm spectroscopy

• L. Zhang

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Introduction

• L. Zhang

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PRL 91 (2003) 262001

X(3872) discovery turned

• ut to be the harbinger of

a new direction in hadron spectroscopy

• S. Olsen, arXiv:1511.01589

X(3860)

Charmonium spectroscopy

Above open charm threshold:

• many expected states not observed
• many unexpected observed

X(3915) X(4140) Y(4260) Y(4360) Y(4660) ... X(3872) Z(4430) Z(4050) Z(4250) Z(3900) Z(4020) Z(4200) Since then, more than 20 non-standard hadrons that contain 𝑑𝑑̅ or 𝑐𝑐 + quarks have been found and studied, called XYZ states

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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

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Pentaquarks

• bserved in 𝛭;

< →

𝐾/𝜔𝑞𝐿# decays

𝑛?/@A (GeV)

PRL115 (2015) 072001 PRL117 (2016) 082002

𝑸𝒅 𝟓𝟓𝟔𝟏 - 𝑸𝒅 𝟓𝟒𝟗𝟏 -

Charged 𝒂𝒅 𝟒𝟘𝟏𝟏 -

• bserved in 𝑍(4260) decays

PRL110 (2013) 252001 PRL110 (2013) 252002

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Experimental methods for XYZ states

𝒀 𝟒𝟗𝟖𝟑 𝒀 𝟒𝟘𝟐𝟔 𝒀 𝟓𝟐𝟓𝟏 𝒀 𝟓𝟑𝟖𝟓 𝒀 𝟓𝟔𝟏𝟏 𝒀 𝟓𝟖𝟏𝟏 𝒂 𝟓𝟓𝟒𝟏 - 𝒂 𝟓𝟏𝟔𝟏 - 𝒂 𝟓𝟑𝟔𝟏 - 𝒂𝒅 𝟓𝟑𝟏𝟏 - 𝑸𝒅 𝟓𝟒𝟗𝟏 - 𝑸𝒅 𝟓𝟓𝟔𝟏 - 𝒀 𝟒𝟘𝟓𝟏 𝒀 𝟓𝟐𝟕𝟏 𝒀(𝟒𝟗𝟕𝟏) 𝒁 𝟓𝟑𝟕𝟏 𝒁 𝟓𝟑𝟑𝟏 𝒁(𝟓𝟒𝟕𝟏) 𝒁(𝟓𝟒𝟘𝟏) 𝒁(𝟓𝟕𝟕𝟏) 𝒁𝒄(𝟐𝟏𝟗𝟕𝟏) 𝒀 𝟒𝟘𝟐𝟔 𝒀 𝟓𝟒𝟔𝟏 𝒂𝒅 𝟒𝟘𝟏𝟏 -,𝟏 𝒂𝒅 𝟓𝟏𝟑𝟏 -,𝟏 𝒂𝒄 𝟐𝟏𝟕𝟐𝟏 -,𝟏 𝒂𝒄 𝟐𝟏𝟕𝟔𝟏 -

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B-factories：

q

Main suppliers of new information about quarkonium states for the last decade

n

Charm-t factories：

q

Extensively studied charmonium states

n

Hadron machines:

q

Prompt quarkonium production in high energy

q

Charmonium produced in B-decays

1##

Υ;(10860)

𝑑, 𝑐

𝐷 = +

𝐟𝐰𝐟𝐨 ±- or 𝐩𝐞𝐞 ≠ 𝟐 -- Modified from [HX Chen et. al. Phys. Rep. 639 (2016) 1]

Color indicates as first observation

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X(3872)

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What is the X(3872)?

n Mass: Very close to 𝐸

c<𝐸∗< threshold

n Width: Very narrow, < 1.2 MeV n 𝐾ef = 1-- n Production

q In 𝑞̅𝑞/𝑞𝑞 collision – rate similar to 𝑑𝑑̅ q In B decays – KX similar to 𝑑𝑑̅, K*X smaller

than 𝑑𝑑̅

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)

q Mixture of 𝜓&o(2𝑄) and 𝐸

c<𝐸∗< bound state?

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X(3872) 36±7 events y(2S) PRL 91 (2003) 262001 PRL 93 (2004) 072001 PRL 93 (2004) 162002

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Observation of X(3872)→ 𝝆𝟏𝝍𝒅𝟐

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5.2s 𝝆𝟏𝝍𝒅𝟏 𝝆𝟏𝝍𝒅𝟐 𝝆𝟏𝝍𝒅𝟑

l

The large value for R1 disfavors the 𝝍𝒅𝟐(𝟑𝑸) interpretation for X(3872)

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Y(4260)

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BES II R value

n 𝑆 =

s(tutv→wxyz{|}) s(tutv→~u~v)

n BES measured

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BES, PLB 660 (2008) 315 𝜔(3770) 𝜔(4040) 𝜔(4160) 𝜔(4415)

𝜔(4160): 𝜔o(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

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The Y states

Y(4360) Y(4660) PRD 91 (2015) 112007

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PRD 86 (2012) 051102(R)

Y(4260)?

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Fine structures in Y(4260)

PRL 118 (2017) 092001

𝞽(𝑓+𝑓−→𝜌+𝜌−ℎ𝑑)

PRL 118 (2017) 092002

𝞽(𝑓+𝑓−→𝜌+𝜌−𝑲/𝝎) 𝞽(𝑓+𝑓−→𝜌+𝜌−𝑲/𝝎)

arXiv:1808.02847

𝞽(𝑓+𝑓−→ 𝝆-𝑬𝟏𝑬∗#)

PRD 96 (2017) 032004

𝞽(𝑓+𝑓−→𝝆-𝝆#𝝎(𝟑𝑻))

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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

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Open question: Y(4220) & Y(4390) are y(4160) and y(4415) seen in hadronic final states?

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Evidence of a 𝒂𝐝

# → 𝜽𝒅𝝆# resonance

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𝜽𝒅𝝆# resonance in 𝑪𝟏 → 𝜽𝒅𝑳-𝝆#

n Charmonium-like charged states 𝑎&

#

q Obviously exotic, since minimal four quark structure

n 𝜃&𝜌# acesses 𝐾e other than 1-, that several 𝑎&

# confirmed to be

q “natural” 𝐾e = 0-, 1# and 2- [ 𝐾 = 𝑀, 𝑄 = −1 Œ ]

d

• S. Olsen, T. Skwarnicki, D. Zieminska, Rev. Mod. Phys. 90 (2018) 15003
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𝑪𝟏 → 𝜽𝒅 𝟐𝑻 𝑳-𝝆#: Signal

𝑪𝟏 mass 𝜽𝒅 mass 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

arXiv:1809.07416

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Dalitz-plot analysis

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

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arXiv:1809.07416

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𝑳∗𝟏 only fit

) [GeV]

−

π

+

K ( m

0.5 1 1.5 2

Candidates / (40 MeV)

100 200 300 400 500

LHCb (a)

3 3.5 4 4.5 5

) [GeV]

−

π S) 1 (

c

η ( m

20 40 60 80 100 120 140 160

Candidates / (40 MeV)

LHCb (c)

3.5 4 4.5 5

) [GeV]

+

S)K 1 (

c

η ( m

20 40 60 80 100 120 140

Candidates / (40 MeV)

LHCb (e) Data Total PDF (1680)

*

K Combinatorial bkg (892)

*

K (1410)

*

K (NR) bkg

−

π

+

K p p → B S-wave

−

π

+

K (1430)

2 *

K

arXiv:1809.07416

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𝑳∗𝟏 + 𝒂𝒅

# fit

) [GeV]

−

π

+

K ( m

0.5 1 1.5 2

Candidates / (40 MeV)

100 200 300 400 500

LHCb (a)

3 3.5 4 4.5 5

) [GeV]

−

π S) 1 (

c

η ( m

20 40 60 80 100 120 140 160

Candidates / (40 MeV)

LHCb (c)

3.5 4 4.5 5

) [GeV]

+

S)K 1 (

c

η ( m

20 40 60 80 100 120 140

Candidates / (40 MeV)

LHCb (e) Data Total PDF (1680)

*

K Combinatorial bkg (892)

*

K (1410)

*

K (NR) bkg

−

π

+

K p p → B S-wave

−

π

+

K (1430)

2 *

K

−

(4100)

c

Z

arXiv:1809.07416

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Evidence for an exotic 𝒂𝒅 𝟓𝟐𝟏𝟏 #

n Adding a 𝑎&

# improve the fit −2 ln ℒ by 22.8, 41.4 and 7.0 for “natural”

𝐾e = 0-, 1# and 2-

n Significance is 3.4𝜏 after considering systematics n 𝐾e = 1# and 0- are both consistent with the data n 𝑛< = 4096 ± 20#˜˜

• o™ MeV and Γ = 152 ± 58#›œ
• •< MeV

n Fit fraction of 𝑎& 4100 # is 3.3 ± 1.1#o.o

• o.˜ %

arXiv:1809.07416

ℬ 𝐶< → 𝑎& 4100 #𝐿-, 𝑎& 4100 # → 𝜃&(1𝑇)𝜌# = (1.89 ± 0.64#<.•¡

• <.¡›)×10#œ

Could it be 0- 𝑎 4050 # → 𝜓&o 𝜌# from 𝐶< decays seen by Belle?

𝑛< 4050 = 4051#£<

• ˜£ MeV

Γ 4050 = 82#˜™

• œ< MeV

PR D85 (2008) 052003

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Doubly-charmed baryon

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c c

d

c c

u

𝛰&&

• 𝛰&&

SLIDE 22

SELEX results on 𝜪𝒅𝒅

• n Observation of 𝛰&&
• (𝑑𝑑𝑒) reported by SELEX

q Mass: 3518.7 ± 1.7 MeV q Short lifetime: 𝝊 𝜪𝒅𝒅

• < 𝟒𝟒 fs @90% CL, but not zero

q Large production: 𝑺 =

𝝉 𝜪𝒅𝒅

u ×𝐂𝐆(𝜪𝒅𝒅 u →𝜧𝒅 u𝑳v𝝆u)

𝝉(𝜧𝒅

u)

∼ 𝟑𝟏%

n Not confirmed by Babar [PRD 74 (2006) 011103], Belle [PRL 97(2006) 162001]

nor LHCb [JHEP 12 (2013) 090]

𝜪𝒅𝒅

• → 𝜧𝒅
• 𝑳#𝝆- PRL 89 (2002) 112001

Nsig = 15.9 6.3s

PLB 628 (2005) 18

𝜪𝒅𝒅

• → 𝒒𝑬-𝝆#

Nsig = 5.6 4.8s SELEX SELEX

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!" = 1 2

&

SLIDE 23

Observation of 𝜪𝒅𝒅

• - from two decay modes

n Expect 𝛰&&

• - has

higher sensitivity at LHCb due to longer lifetime

n Observed two decay

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

5.9s

PRL 121 (2018) 162002

𝑶𝐭𝐣𝐡 = 𝟘𝟐 ± 𝟑𝟏

PRL 119 (2017) 112001

12s

𝑶𝐭𝐣𝐡 = 𝟒𝟐𝟒 ± 𝟒𝟒

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SLIDE 24

3618 3620 3622 3624 3618 3620 3622 3624

M(Ξ ++

cc )

⇥ MeV/c2⇤ LHCb Ξ ++

cc

→ Λ +

c K−π+π+

Ξ ++

cc

→ Ξ +

c π+

Combined

𝟒𝟕𝟑𝟐. 𝟓𝟏 ± 𝟏. 𝟖𝟑 ± 𝟏. 𝟑𝟖 ± 𝟏. 𝟐𝟓(𝜧𝒅

• ) MeV/c2

𝟒𝟕𝟑𝟏. 𝟔𝟕 ± 𝟐. 𝟔 ± 𝟏. 𝟓 ± 𝟏. 𝟒(𝜪𝒅

• ) MeV/c2

𝟒𝟕𝟑𝟐. 𝟑𝟓 ± 𝟏. 𝟕𝟔 ± 𝟏. 𝟒𝟐 MeV/c2

Observation of new decay mode 𝜪𝒅𝒅

• - → 𝜪𝒅
• 𝝆-

n Consistent mass measurements n Ratio of branching fractions

𝓢 = 𝓒(𝜪𝒅𝒅

• - → 𝜪𝒅
• 𝝆-; 𝜪𝒅
• → 𝒒𝑳#𝝆-)

𝓒(𝜪𝒅𝒅

• - → 𝜧𝒅
• 𝑳#𝝆-𝝆-; 𝜧𝒅
• → 𝒒𝑳#𝝆-) = 𝟒. 𝟔 ± 𝟏. 𝟘 ± 𝟏. 𝟒 ×𝟐𝟏#𝟑

Consistent with prediction [Yu et al., arXiv:1703.09086, CPC 42 (2018) 051001]

PRL 121 (2018) 162002

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Mass difference: 𝑛(Ξ&&

• -)LHCb − 𝑛(𝛰&&
• )SELEX = 103 ± 2 MeV

ØInconsistent with being isospin partners

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Decay time [ps]

0.5 1 1.5 2

Candidates / (0.095 ps)

10 20 30 40 50 60

LHCb

Data Fit

First measurement of 𝜪𝒅𝒅

• - lifetime

n Using 𝜪𝒅𝒅

• - → 𝜧𝒅
• 𝑳#𝝆-𝝆- decays

𝝊𝚶𝒅𝒅

uu = 𝟑𝟔𝟕#𝟑𝟑

• 𝟑𝟓 ± 𝟐𝟓 fs

PRL 121 (2018) 152002

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Confirmed it is weakly decaying J = ½ ground state

Precision 10.5%

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New results on bottom and charm spectroscopy

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𝜪𝒄 baryon spectroscopy

n Numbers of excited b-baryons have already

been discovered

q 𝛰;

∗ 5945 < → 𝛰; #𝜌- [CMS’12]

q 𝛰;

¼ 5935 #, 𝛰; ∗ 5955 # → 𝛰; <𝜌# [LHCb’15]

q 𝛰;

¼ < not yet observed

State 𝑲𝑸 𝑐 𝑡𝑟 𝜪𝒄 𝟐/𝟑- ↑ ↑↓ 𝜪𝒄

¼

𝟐/𝟑- ↓ (↑↑) 𝜪𝒄

∗

𝟒/𝟑- ↑ (↑↑)

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no 𝜪𝒄

¼𝟏

PRL 108, 252002 (2012)

𝜪𝒄

∗ 𝟔𝟘𝟓𝟔 𝟏

𝜪𝒄

∗ 𝟔𝟘𝟓𝟔 𝟏

𝑵 𝜪𝒄

#𝝆- − 𝑵 𝜪𝒄 # − 𝑵(𝝆-) [MeV/c2]

JHEP 05 (2016) 161

𝜪𝒄

¼ 𝟔𝟘𝟒𝟔 #

𝜪𝒄

∗ 𝟔𝟘𝟔𝟔 #

𝑵 𝜪𝒄

𝟏𝝆# − 𝑵 𝜪𝒄 𝟏 − 𝑵(𝝆#) [MeV/c2]

PRL 114 (2015) 062004

Charged 𝛰;

¼(∗)

Neutral 𝛰;

∗

SLIDE 28

Observation of a new 𝜪𝒄

∗∗ 𝟕𝟑𝟑𝟖 # state

n Reconstruct 𝛰;

# → 𝛭; <𝐿# and 𝛰; <𝜌-

q Hadronic decays (HD) and Semileptonic (SL) decays for 𝛭;

<

q SL decays for 𝛰;

< → 𝛰&

• 𝜈#𝜉̅~

PRL 121 (2018) 072002

𝛭;

<𝐿# (HD)

𝛭;

<𝐿# (SL)

𝛰;

<𝜌- (SL)

n With hadronic mode n Production ratios are measured with SL modes

q Useful for theoretical interpretation

Mass peak position is consistent between the three decay channels

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New method using SL gives 15x yield than that in HD Will largely increase exploration power of excited bottom hadrons

25s 8s 9s

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𝜯𝒄 spectroscopy: Observation of 𝜯𝒄 𝟕𝟏𝟘𝟖 ±

n 𝛭;

< → 𝛭&

• 𝜌# combined with 𝜌± from PV

n 𝑞Ä 𝜌± > 1 GeV to suppress backgd n Relativistic BW convoluted with

resolutions of 1.0, 1.1, 2.4 MeV for 𝛵;, 𝛵;

∗, 𝜯𝒄 𝟕𝟏𝟘𝟖

𝜯𝒄 𝟕𝟏𝟘𝟖 # [𝒄𝒆𝒆] 𝜯𝒄 𝟕𝟏𝟘𝟖 - [𝒄𝒗𝒗]

𝜯𝒄

± and 𝜯𝒄 ∗± parameters are measured,

5x more precise than the previous CDF values

Arxiv:1809.07752

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Excited 𝜵𝒅 states

n LHCb observed 5 narrow states (+ a possible wide one) in 2017 n Belle confirmed the first four states this year PRL 118 (2017) 182001 PRD 97 (2018) 051102

The measured masses are consistent with LHCb values

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SLIDE 31

Measurement of absolute Brs of 𝜪𝒅

𝟏

n 𝛰&

< → 𝑞𝐿#𝐿#𝜌- play a fundamental role in studies of b-baryons at LHCb

n Belle used a novel method

q With full B-tag Measure inclusive 𝓒(𝑪# → 𝚳𝒅

#𝜪𝒅 𝟏, 𝜪𝒅 𝟏 → 𝐛𝐨𝐳𝐮𝐢𝐣𝐨𝐡), never measured before

q Then measure exclusive 𝓒(𝑪# → 𝚳𝒅

#𝜪𝒅 𝟏, 𝜪𝒅 𝟏 → 𝐭𝐪𝐟𝐠𝐣𝐝 𝐞𝐟𝐝𝐛𝐳)

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See Chenping’s talk at Wednesday’s HS parallel session

SLIDE 32

LHCb Upgrade 1

32

Belle II 9 fb-1

Phase 1b Upgrade

LHCb ~50 fb-1

Phase 2 Upgrade Phase 2

300 fb-1

Phase 1b

9

55 10 BB pairs » ´

12

3 10 pairs bb » ´

50 ab-1

2025 2020 2030 2035 2018

Phase I

~23 fb-1

Future

BES III Continue to run for 8-10 years Increase Ecm=> 4.9 GeV For more Belle result, see Kenkichi Miyabayashi’s talk “Belle-II project” next (proposed)

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Summary

n Recent experiments have made important progress on exotic states

q Many states were observed q However synergy between theorists and experimentalists is greatly needed

to decipher their nature

n Belle (II), BES III and LHCb are complementary to each other

q Many states observed by B-factories, are extensively studied by BESIII and

LHCb, and new states are further observed

n LHCb shows unique power to explore heavier states:

q including excited b-baryons, doubly-heavy baryons & exotic baryons

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SLIDE 34

Backup

SLIDE 35

Introduction

n QCD describing strong interaction between quarks and gluons is not well

understood due to its non-perturbative nature at low energy scale

n Hadron spectroscopy provides opportunities to study QCD predictions from

models

q e.g. lattice QCD, diquark model, potential model …

n Exotic states are important for understanding strong force in QCD

q Predicted in quark model q Recent results show strong evidence for their existence

mesonic molecule ? pentaquark ? tetraquark ? hybrid ?

…

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Mass and lifetime predictions vs measurements

n Predicted 𝛰&&

• ,-- masses in range 3.5 − 3.7 GeV

n Mass splitting between 𝛰&&

• and 𝛰&&
• - only a few MeV due to 𝑣, 𝑒 symmetry

n Expectation: 𝜐(𝛰&&

• -) ≃ 4×𝜐(𝛰&&
• )

n Calculations give 𝜐 𝛰&&

• - ∈ [ 200 − 1550] fs

SELEX 𝜪𝒅𝒅

• LHCb 𝜪𝒅𝒅
• fs

200 400 600 800 1000 1200 1400 1600

LHCb 𝜪𝒅𝒅

• Measured lifetime at low side of predictions

Ref # Ref #

• L. Zhang

36

SLIDE 37

• L. Zhang

37

SLIDE 38

Search for 𝒀𝒄𝒄𝒄

c𝒄 c → 𝚽 𝟐𝑻 𝝂-𝝂#

• L. Zhang

38

JHEP 10 (2018) 086

SLIDE 39

𝝍𝒅𝟐 𝟓𝟔𝟒 ± 𝟑𝟔 𝝍𝒅𝟑 𝟑𝟗𝟔 ± 𝟑𝟒

Observation of 𝜧𝒄

𝟏 → 𝝍𝒅(𝟐,𝟑)𝒒𝑳#

n Search for 𝑄

& 4450 -in 𝜧𝒄 𝟏 → 𝝍𝒅(𝟐,𝟑)𝒒 𝑳#decays

⇒Test hypothesis of kinematic rescattering effect

n First step: observe the decays, measure ℬ n Use 𝜓&(o,˜) → 𝐾/𝜔𝛿, constrain 𝐾/𝜔𝛿 mass to known 𝜓&o mass

PRD 92 (2015) 071502 𝓒(𝜧𝒄

𝟏 → 𝝍𝒅𝟐𝒒𝑳#)

𝓒(𝜧𝒄

𝟏 → 𝑲/𝝎𝒒𝑳#) =

𝟏. 𝟑𝟓𝟑 ± 𝟏. 𝟏𝟐𝟓 ± 𝟏. 𝟏𝟐𝟒 ± 𝟏. 𝟏𝟏𝟘 𝓒(𝜧𝒄

𝟏 → 𝝍𝒅𝟑𝒒𝑳#)

𝓒(𝜧𝒄

𝟏 → 𝑲/𝝎𝒒𝑳#) =

𝟏. 𝟑𝟓𝟗 ± 𝟏. 𝟏𝟑𝟏 ± 𝟏. 𝟏𝟐𝟓 ± 𝟏. 𝟏𝟏𝟘 𝓒(𝝍𝒅𝑲) PRL 119 (2017) 062001 7+8 TeV

Next step: full amplitude analysis with more data

• L. Zhang

39

SLIDE 40

5700 5800 5900 20 40

Data Total fit signal

• b

Ξ

• K

Σ ψ J/

• Comb. bkg

LHCb LL

5700 5800 5900

4 − 2 − 2 4

5700 5800 5900 20 40 60 80

LHCb DD

5700 5800 5900

4 −2 −0 2 4

]

2

c ) [MeV/

−

K Λ ψ m(J/ )

2

c Candidates/(6 MeV/

Observation of 𝜪𝒄

#→ 𝑲/𝝎𝜧𝑳#

n Strange pentaquark (𝒗𝒆𝒕𝒅𝒅

+) predicted in

[PRL 105 (2010) 232001]

n Can be searched for in the 𝛰;

# decay [PRC 93 (2016) 065203]

s s !"

#

PLB 772 (2017) 265-273 Nsig = 𝟒𝟏𝟗 ± 𝟑𝟐 (21s) (4.19 ± 0.29 ± 0.15)×10-2

𝜧 decays in vertex detector 𝜧 decays after vertex detector

7+8 TeV Expect ~1500 signals after 2018 for amplitude analysis

• L. Zhang

40

SLIDE 41

Weakly decaying b-flavoured pentaquarks

n Skyrme model: heavy quarks give

tightly bound pentaquark

n Search for mass peaks below strong

decay threshold

n Upper limit on production ratio 𝜏 ⋅ ℬ wrt 𝛭;

< → 𝐾/𝜔𝐿#𝑞

PLB 590(2004) 185; PLB 586(2004)337; PLB 331(1994)362 PRD 97 (2018) 032010

+

d u b u d d c u u d

}

}p

}

c s

ψ J/ K

figure by Stone

(a)

{

PB p

+

u u}

+

π−

• L. Zhang

41

SLIDE 42

Weakly decaying b-flavoured pentaquarks

n No evidence for signal, 90% CL limits on 𝑆 < 10#˜ − 10#›

7+8 TeV

PRD 97 (2018) 032010

• L. Zhang

42

SLIDE 43

5550 5600 5650 5700

]

2

c ) [MeV/

−

π p p

+ c

Λ m(

50 100 150 200

)

2

c Candidates / ( 4 MeV/

LHCb (a)

Data Total

−

π p p

+ c

Λ →

b

Λ Background

Search for dibaryon state

n A dibaryon state 𝑑𝑒 𝑣𝑒 [𝑣𝑒]

could be produced in 𝛭;

< decays

to final state 𝛭&

• 𝜌#𝑞𝑞̅

n LHCb has discovered the decay

𝛭;

< → 𝛭&

• 𝜌#𝑞𝑞̅

¯ u ¯ u ¯ d d u d c u d b u d W − Λ0

b

¯ p D+

c → "#

$%&'

926±43 signal

Resonance contributions 7+8 TeV

• L. Maiani, et al. PLB 750 (2015) 37

LHCb-PAPER-2018-005 arXiv:1804.09617 submitted to PLB

2500 2600 2700

]

2

c ) [MeV/

−

π

+ c

Λ m(

10 20 30 40

)

2

c Candidates / ( 3 MeV/

LHCb

c

Σ

*0 c

Σ

Data Total Background

−

π

+ c

Λ →

c

Σ

−

π

+ c

Λ →

*0 c

Σ

• L. Zhang

43

SLIDE 44

Search for dibaryon state

n Ratio of branching fractions n No obvious dibaryon peak in 𝑛(𝛭&

• 𝜌#𝑞) spectra

LHCb-PAPER-2018-005 arXiv:1804.09617 submitted to PLB

All signals 𝛵&

< region signals

𝛵&

∗< region signals

3500 4000 4500

]

2

c ) [MeV/ p

−

π

+ c

Λ m(

20 40 60

)

2

c Entries/(25 MeV/

Data Simulation

LHCb (a)

]

2

c ) [MeV/ p

−

π

+ c

Λ m(

3500 4000 4500

)

2

c Entries/(25 MeV/

2 4 6

LHCb (b)

]

2

c ) [MeV/ p

−

π

+ c

Λ m(

3500 4000 4500

)

2

c Entries/(25 MeV/

5 10

LHCb (c)

• L. Zhang

44

SLIDE 45

Observation of a new 𝛰;

∗∗# state

n Hadronic 𝛭;

< → 𝛭&

• 𝜌#:

q Resolution: 2 MeV q 7.9s

n Semileptonic (SL)

𝛭;

< → 𝛭&

• 𝜈#𝜉̅~

q Resolution: ~18 MeV q Yields ~15 larger q 25s

n Semileptonic (SL)

𝛰;

< → 𝛰&

• 𝜈#𝜉̅~

q 9.2s

PRL 121 (2018) 072002

• L. Zhang

45

SLIDE 46

BESIII data samples

• L. Zhang

46

SLIDE 47

Cross sections of 𝑓+𝑓−→𝜕/𝜚𝜓𝑑J (J=0,1,2)

• Phys. Rev. D 93, 011102 (2016)

The triangle black data points are from

• Phys. Rev. Lett. 114,092003(2015)

Other data points are from >9𝝉

e+e-à wc wcc0: Fit with a single BW Mass = 4226±8±6 MeV Width = 39±12±2 MeV Significance > 9𝞽 e+e-à wc wcc2: Agree with from y(4415) with BR=(1.4±0.5)×10-3 (sol. I), or BR=(6±1)×10-3 (sol. II) Need data beyond 4.6 GeV to check structure in wc wcc1 and 𝝔𝝍𝒅𝑲

While BESIII measures 𝐟-𝐟# → 𝜚𝜓𝑑J at 4.6GeV

• 𝜏 𝑓-𝑓# → 𝜚𝜓&< < 5.4 pb
• 𝜏 𝑓-𝑓# → 𝜚𝜓&o < (4.2#o.<
• o.¡ ± 0.3) pb
• 𝜏 𝑓-𝑓# → 𝜚𝜓&˜ < (6.7#o.¡
• ›.£ ± 0.5) pb

PRD97, 032008 (2018)

• L. Zhang

47

SLIDE 48

Y(4220) and the new Y's

"Y(4220)"𝝏𝝍𝒅𝟏

• L. Zhang

48

SLIDE 49

The Zc Family at

Which is the nature of these states? Different decay channels of the same observed states? Other decay modes?

• L. Zhang

49

Zc Zc(3 (3885)+? Zc Zc(3 (3885)0? Zc Zc(3 (3900)+? Zc Zc(3 (3900)0? Zc Zc(4 (4025)+? Zc Zc(4 (4025)0? Zc Zc(4 (4020)+? Zc Zc(4 (4020)0?

𝒇-𝒇# → 𝝆𝟏(𝑬∗𝑬 c∗)𝟏 𝒇-𝒇# → 𝝆𝟏(𝑬∗𝑬 c )𝟏 PRL 110, 252001 (2013) PRL 115, 222002 (2015) PRL115, 182002 (2015) PRL 112, 132001 (2014) ST: PRL 112, 022001(2014) DT: PRD92, 092006 (2015) PRL 115, 112003 (2015) PRL 111, 242001(2013) PRL113,212002 (2014)

SLIDE 50

𝒇-𝒇# → 𝝎 𝟑𝑻 𝝆-𝝆# Dalitz-plot

2

)

2

) (GeV/c

±

π (3686) ψ (

2

M

15.0 15.5 16.0 16.5

2

)

2

) (GeV/c

• π

+

π (

2

M

0.0 0.1 0.2 0.3 2 4 6 8 10

2

)

2

) (GeV/c

±

π (3686) ψ (

2

M

15.0 15.5 16.0 16.5 17.0

2

)

2

) (GeV/c

• π

+

π (

2

M

0.0 0.1 0.2 0.3 0.4 2 4 6 8

2

)

2

) (GeV/c

±

π (3686) ψ (

2

M

15 16 17

2

)

2

) (GeV/c

• π

+

π (

2

M

0.0 0.1 0.2 0.3 0.4 0.5 2 4 6 8 10 12

2

)

2

) (GeV/c

±

π (3686) ψ (

2

M

15 16 17 18

2

)

2

) (GeV/c

• π

+

π (

2

M

0.0 0.2 0.4 0.6 5 10 15 20

2

)

2

(3686))(GeV/c ψ

±

π (

2

M

15.0 15.5 16.0 16.5

)

2

)

2

Events / (0.1 (GeV/c

20 40 60 80

2

)

2

(3686))(GeV/c ψ

±

π (

2

M

15.0 15.5 16.0 16.5

)

2

)

2

Events / (0.1 (GeV/c

20 40 60

2

)

2

(3686))(GeV/c ψ

±

π (

2

M

15 16 17

)

2

)

2

Events / (0.1 (GeV/c

20 40 60 80

2

)

2

(3686))(GeV/c ψ

±

π (

2

M

15 16 17 18

)

2

)

2

Events / (0.1 (GeV/c

50 100 150

2

)

2

(3686))(GeV/c ψ

±

π (

2

M

15 16 17 18

)

2

)

2

Events / (0.1 (GeV/c

50 100 150

2

)

2

)(GeV/c

• π

+

π (

2

M

0.10 0.15 0.20 0.25 0.30

)

2

)

2

Events / (0.01 (GeV/c

10 20 30 40

2

)

2

)(GeV/c

• π

+

π (

2

M

0.10 0.15 0.20 0.25 0.30

)

2

)

2

Events / (0.01 (GeV/c

10 20 30

2

)

2

)(GeV/c

• π

+

π (

2

M

0.1 0.2 0.3 0.4

)

2

)

2

Events / (0.01 (GeV/c

20 40 60

2

)

2

)(GeV/c

• π

+

π (

2

M

0.1 0.2 0.3 0.4 0.5

)

2

)

2

Events / (0.02 (GeV/c

20 40 60

2

)

2

)(GeV/c

• π

+

π (

2

M

0.1 0.2 0.3 0.4 0.5

)

2

)

2

Events / (0.02 (GeV/c

20 40 60

PRD 96 (2017) 032004

• L. Zhang

50

SLIDE 51

LHCb results on tetra and pentaquarks

]

2

[GeV

2

−

π ' ψ

m 16 18 20 22 )

2

Candidates / ( 0.2 GeV 500 1000

LHCb

[MeV]

φ ψ J/

m

4100 4200 4300 4400 4500 4600 4700 4800 Candidates/(10 MeV) 20 40 60 80 100 120

LHCb

X(4140) 8.4s X(4274) 6.0s X(4500) 6.1s X(4700) 5.6s

n

Confirmation of 𝑎(4430)

n

Observation of two charmonium pentaquarks

n

Observation of four 𝐾/𝜔𝜚 structures

n

Evidence of exotic contribution in Cabibbo- suppressed decays

Without Z(4430)- Data Fit

!" #$%& '

!" ##(& '

)*/,- [012]

PRL 115 (2015) 072001

mpp>1.8 GeV w/o exotics w/ exotics

𝜧𝒄

𝟏 → 𝑲/𝝎𝒒𝑳#

𝜧𝒄

𝟏 → 𝑲/𝝎𝒒𝝆#

PRL 117 (2016) 082003

𝑪𝟏 → 𝝎 𝟑𝑻 𝝆#𝑳- 𝑪- → 𝑲/𝝎𝝔𝑳-

PRL 118 (2017) 022003 PRL 112 (2014) 222002

• L. Zhang

51

SLIDE 52

• L. Zhang

52

SLIDE 53

Doubly charmed baryons: motivation

n Doubly charmed baryons are not observed or

established

n Doubly heavy baryons’ mass and decay width to test

QCD motivated models

n Baryons with two heavy quarks probe the QCD

potential in a different way than baryons with a single heavy quark [hep-ph/9811212]

q HQET: two charm quarks considered as a heavy diquark,

doubly heavy baryon similar to a heavy meson 𝑹 c𝒓

q Such diquark can naturally extend to 𝑹

c𝒓 c𝒓 c = 𝒅𝒅𝒓 c𝒓 c exotic system

𝒅

𝒓

diquark

𝒅

!" = 1 2

&

• L. Zhang

53

SLIDE 54

Theoretical interpretations

n 𝛰;

∗∗ 6227 #: good candidate for 1P 5/2- or 3/2- state

q Not 2S state, since 2S state doesn’t decay into 𝛭;𝐿

n 𝛵; 6097 ± : good candidates for 1P 5/2- or 3/2- state

Bing Chen, Xiang Liu arxiv:1810.00389 Bing Chen et. al. PRD 98 (2018) 031502(R)

• L. Zhang

54

SLIDE 55

Measurement of 𝜵𝒅

𝟏 lifetime

n Charm-hadron lifetimes probe high-

• rder corrections in HQE

n Charm-baryon lifetimes are not well

measured, in particular 𝛻&

< (69 ± 12 fs)

n Current measurements n LHCb uses 𝑐 → 𝑑 semileptonic decays

to avoid bias on charm

q Signal: 𝜵𝒄

# → 𝜵𝒅 𝟏(→ 𝒒𝑳#𝑳#𝝆-)𝝂#𝝃

c𝝂𝒀

q Control: 𝑪 → 𝑬-(→ 𝑳#𝝆-𝝆-)𝝂#𝝃

c𝝂𝒀

7+8 TeV Yields: 𝛁𝒅

𝟏𝝂#: 𝟘𝟖𝟗 ± 𝟕𝟏

(~10 times larger than any previous sample used for 𝝊) PRL 121 (2018) 092003

• L. Zhang

55

Precision 17%

SLIDE 56

𝜵𝒅

𝟏 lifetime result

n Simultaneous fit signal and control samples n Many cross-checks

q 13 TeV 2016 data q An additional 𝐸< → 𝐿3𝜌 lifetime measurement

n LHCb result gives

𝝊𝜵𝒅

𝟏

𝝊𝑬u = 𝟏. 𝟑𝟔𝟗 ± 𝟏. 𝟏𝟑𝟒 ± 𝟏. 𝟏𝟐𝟏 𝝊𝜵𝒅

𝟏 = 𝟑𝟕𝟗 ± 𝟑𝟓 ± 𝟐𝟏 ± 𝟑 (𝝊𝑬u) fs

Precision 9.7%

decay time [ps]

c

Ω

0.2 0.4 0.6

Signal yield / 0.04 ps

50 100 150 LHCb

X ν

−

µ

c

Ω →

− b

Ω

Data Fit =69 fs τ

(PDG)

PRL 121 (2018) 092003 lifetime [fs]

c

Ω

200 400

E687 [1995] WA89 [1995] FOCUS [2003] X ν

−

µ

c

Ω →

− b

Ω LHCb,

+

π

−

K

−

pK →

c

Ω PDG Average

𝟕𝟘 ± 𝟐𝟑 fs 4× larger than PDG value

Verifications are needed from the other experiments and LHCb study using prompt 𝜵𝒅

𝟏

• L. Zhang

56