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

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Introduction

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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&&

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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

&

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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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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;

∗

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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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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

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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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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 #

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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