Mini-Worskshop Bled 2013, Looking into Hadrons 9 July 2013

(1)

Marko Pet!č

on behalf of the Belle Collaboration

Mini-Worskshop Bled 2013, Looking into Hadrons

9 July 2013

Marko Petrič marko.petric@ijs.si Spectroscopy and Resonances at B-Factories 1/51

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Content

• The experiment

• Botomonium

◦ Observation of exotic states Z

_b

states

◦ Observation of Υ(5S) → Υ(nS)π

⁰

π

⁰

◦ 6D amplitude analysis of Υ(5S) → Υ(nS)π

⁺

π

⁺

◦ h

_b

→ η

b

transitions

◦ First Evidence for η

b

(2S)

• Chamonium

◦ Update on e

⁺

e

⁻

→ π

⁺

π

⁻

J/ψ via initial state radiation (ISR)

◦ Update on e

⁺

e

⁻

→ π

⁺

π

⁻

ψ(2S) via ISR

◦ e

⁺

e

⁻

→ ηJψ via ISR

◦ Measurement of Z (4430)

⁺

quantum numbers

◦ Updated results of Y (4008) and Y (4260)

• Look into the future

2

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The Factories

Aerogel Cherenkov cnt.

SC solenoid CsI TOF Counter

SVD µ/KLdetector

Central Drift Chamber

�.� GeVe⁺

�.� GeVe

Christian Oswald – Spectroscopy from the and incl. semileptonic - BEAUTY 2013 7

data sample

20%

76%

4%

Background for studies, but interesting for spectroscopy Initial motivation to take data near

Bottomonium spectroscopy

[PRL102,012001(2009)]

e

⁺

e

⁻

colliders particularly clean environment for spectroscopy

Very clean environment for physics studies

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The Υ(5 S ) data sample

• Heavy quarkonium is an ideal tool to study the “meson”

which carries spin and angular momentum and described by (mostly non-relativistic) QCD. Godfrey-Isgur, PRD32,169(1985)

data sample

20%

76%

4%

Background for studies, but interesting for spectroscopy Initial motivation to take data near

Bottomonium spectroscopy

[PRL102,012001(2009)]

B

^{( )}_s

B

^{( )}_s

B

^{( )}

B

^{( )}

( ) (bb)X

��

(�S) ��

• Initial motivation to take data near Υ(5 S )

• Background for B

s

studies, but interesting for spectroscopy

• Bottomonium spectroscopy

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Puzzles of Υ(5 S ) Decays

Very interesting but yet understood

R

_b

and σ(Υ(nS)ππ) shapes are different (2σ)

(GeV) s

10.75 10.8 10.85 10.9 10.95 11 11.05

]µµ[0σ] / ππ(nS)Υ[σ

0.000 0.002 0.004 0.006 0.008 0.010 0.012

π π (1S) Υ

π π (2S) Υ

π (3S)π Υ

(GeV) s

10.75 10.8 10.85 10.9 10.95 11 11.05

]µµ[0σ] / b[bσ = bR

0.1 0.2 0.3 0.4 0.5 0.6

(a)

PRD82, 091106R(2010)

Anomalously Υ(nS )ππ transitions at Belle

Process Γ[MeV]

Υ(5S)→Υ(1S)π⁺π⁻ 0.59±0.04±0.09 Υ(5S)→Υ(2S)π⁺π⁻ 0.85±0.07±0.16 Υ(5S)→Υ(3S)π⁺π⁻ 0.52^+0.20_−0.17±0.10 Υ(2S)→Υ(1S)π⁺π⁻ 0.0060 Υ(3S)→Υ(1S)π⁺π⁻ 0.0009 Υ(4S)→Υ(1S)π⁺π⁻ 0.0019

Γ [Υ(5S) → Υ(1, 2, 3, S)π

⁺

π

⁻

]

Γ [Υ(2, 3, 4 S ) → Υ(1 S )π

⁺

π

⁻

] 100

• Rescattering of on-shell B

⁽^∗⁾

B

⁽^∗⁾

[JETP Lett 87, 147 (2008)]

• Tetraquarks [Eur. Phys. J. C71, 1534 (2011)]

• Exotic resonance Y

_b

near Υ(5S) analogue of Y (4260) resonance with Γ ( J /ψππ) [PRL104, 162001 (2010)]

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Observation of Υ(5 S ) → h _b ( nP )π ⁺ π ⁻

h

b

(nP)

e

⁺

e

+

(�S)

Belle: Inclusive search e

⁺

e

⁻

→ Υ(5 S ) → π

⁺

π

⁻

X M

_miss

(π

⁺

π

⁻

)

²

= (E

Υ(5S)

− E

_ππ

)

²

− p

²_ππ

Simultaneous discovery of h

_b

(1P ) and h

_b

(2P) [PRL 108, 032001 (2012)]

Events / 5 MeV/c2

0 10000 20000 30000 40000

9.4 9.6 9.8 10 10.2 10.4

M_miss(GeV/c ) 2

ϒ(3S)→ϒ(1S) ϒ(2S)→ϒ(1S)

ϒ(1S)

ϒ(2S)

ϒ(3S) ϒ(1D)

h _b(2P) h _b(1P)

Yield [×10³] Mass [MeV/c²] Significance Υ(1S) 105.2±5.8±3.0 9459.4±0.5±1.0 18.2σ h_b(1P) 50.4±7.8^+4.5_−9.1 9898.3±1.1^+1.0_−1.1 6.2σ

3S→1S 56.0±19 9973.01 2.9σ

Υ(2S) 143.5±8.7±6.8 10022.3±0.4±1.0 16.6σ Υ(1D) 22.0±7.8 10166.2±2.6 2.4σ h_b(2P) 84.4±6.8^+23._−10. 10259.8±0.6^+1.4_−1.0 12.4σ 2S→1S 151.7±9.7^+9.0_−20. 10304.6±0.6±1.0 15.7σ Υ(3S) 45.6±5.2±5.1 10356.7±0.9±1.1 8.5σ

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h _b results

• h

_b

is the singlet partner of χ

bJ

(nP )

◦ Hyperfine Splitting: M (singlet ) − M(triplet )

◦ M

swa

= (χ

_bJ

(nP )) = (M

_χ_b0

+ 3M

χb1

+ 5M

χb2

)/9

◦ Deviations from Spin Weighted Average of χ

bJ

consistent with zero [PRL 109, 232002 (2012)]

◦ ∆M

HF

= M(h

b

(nP )) − M

swa

(χ

bJ

(nP)) =

0.8 ± 1.1 MeV 1P 0.5 ± 1.2 MeV 2P

• Heavy quark spin flip should suppress the π

⁺

π

⁻

h

_b

transition

◦ R =

^Γ[Υ(5S)

Spin Flip

−→ h_b(nP)π⁺π⁻] Γ[Υ(5S)No Spin Flip

−→ Υ(2S)π⁺π⁻]

=

0.46 ± 0.08

^+0.07_−0.12

1P 0.77 ± 0.08

^+0.22_−0.17

2P

◦ Violation of heavy quark spin symmetry

• Exotic decay mechanism

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Resonant structure of Υ(5 S ) → h _b (1 P , 2 P )π ⁺ π ⁻

• Belle has discovered two charged bottomonium-like resonances [PRL 108, 122001 (2012)]

Outline

10.50

10.25

10.00

9.75

9.50

Mass [GeV]

Observation of exotic states

Υ(5S)→h_b(1P)π⁺π⁻background subtracted

-2000 0 2000 4000 6000 8000 10000 12000

10.4 10.5 10.6 10.7

M_miss(π), GeV/c²

Events / 10 MeV/c2

(a)

Υ(5S)→h_b(2P)π⁺π⁻background subtracted

0 2500 5000 7500 10000 12500 15000 17500

10.4 10.5 10.6 10.7

M_miss(π), GeV/c²

Events / 10 MeV/c2

(b)

• Saturated with Z

_b

• Non-resonant amplitude constant with zero

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Resonant structure of Υ(5 S ) → Υ( nS )π ⁺ π ⁻

• Charged Z

_b

states are observed in 5 final states

102 104 106 108 110 112 114 116

0 0.5 1 1.5 2

M²(π⁺π^-), GeV²/c⁴ M2(Y(1S)π)max, GeV2/c4

(a)

108 110 112 114 116

0 0.2 0.4 0.6 0.8

(b)

112 113 114 115 116

0 0.1 0.2 0.3

(c)

FIG. 2: Dalitz plots for Υ(nS)π⁺π⁻events in Υ(nS) mass sidebands for the (a) Υ(1S); (b) Υ(2S); (c) Υ(3S)

102 104 106 108 110 112 114 116

0 0.5 1 1.5 2

(a)

108 110 112 114 116

0 0.2 0.4 0.6 0.8

(b)

112 113 114 115 116

0 0.1 0.2 0.3

(c)

FIG. 3: Dalitz plots for Υ(nS)π⁺π⁻events in signal region for the (a) Υ(1S); (b) Υ(2S); (c) Υ(3S). Vertical lines indicate the regions of Dalitz plots included in amplitude analyses.

high background region applying requirement onM(π⁺π⁻) as given in Table I. For the remaining part of the phase space the distribution of background events is assumed to be uniform.

For the further analysis we select events around respective Υ(nS) mass peak as shown in Fig. 1;

Dalitz plots for selected events are shown in Fig. 3. Fractions of signal events in the selected samples are given in Table I were determined from the fit to the correspondingM M(π⁺π⁻) spectrum as described above.

The amplitude analysis of three-body Υ(10860)→Υ(nS)π⁺π⁻(n= 1,2,3) decays reported here is performed by means of an unbinned maximum likelihood fit. Variations of the reconstruction efficiency over the phase space is determined using MC simulated signal events generated to have uniform distribution.

We use the following parametrization of the Υ(10860)→Υ(nS)π⁺π⁻three-body decay amplitude:

M(s1, s2) =A1(s1, s2) +A2(s1, s2) +Af0+Af2+AN R,

wheres1=m²(Y(nS)π⁺),s2=m²(Y(nS)π⁻). AmplitudesA1andA2areS−wave Breit-Wigner functions to account for observedZb(10610) andZb(10650) peaks, respectively. To account for a possibility for Υ(10860) decay to bothZ⁺π⁻andZ⁻π⁺channels, amplitudesA1 andA2 are symmetrized with respect toπ⁺andπ⁻interchange. Taking into account isospin symmetry the

(�S) (�S)⁺ (�S) (�S)⁺ (�S) (�S)⁺

• Region with large backgrounds from photon conversions were excluded

• Signal amplitude parameterization:

S(s1,s2) =A(Z_b1) +A(Z_b2) +A(f₀(980)) +A(f₂(1275)) +C₁^NR+C₂^NRm²(ππ)

• Parameterization of the NR-amplitude: [PRD74, 054022 (2006)]

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Resonant structure of Υ(5 S ) → Υ( nS )π ⁺ π ⁻

Υ(5S)→Υ(1S)π⁺π⁻

0 20 40 60 80

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 M(Y(1S)π)_max, (GeV/c²)

(Events/10 MeV/c2) (a)

0 20 40 60 80 100

10.4 10.45 10.510.55 10.610.65 10.7 10.75 M(Y(2S)π)_max, (GeV/c²)

(Events/5 MeV/c2) (c)

0 20 40 60 80 100 120

10.58 10.62 10.66 10.70 10.74

M(Y(3S)π)_max, (GeV/c²)

(Events/4 MeV/c2) (e)

• Z

_b

amplitudes are parameterized by Breit-Wigner functions and symmetrized with respect to interchange of the two pions: A(Z

b

) = BW (s

1

, M

Z

, ΓZ ) + BW (s

2

, M

Z

, Γ Z )

• A(f

0

(980) – Flatte distribution

• A(f

0

(1275) – Breit-Wigner distribution

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Summary of Z _b masses and widths

Average over 5 channels M

₁

= 10607.2 ± 2.0 MeV Γ

₁

= 18.4 ± 2.4 MeV

M

Z_b

− M

BB^∗

= 2.6 ± 2.1 MeV M

₂

= 10652.2 ± 1.5 MeV Γ

₂

= 11.5 ± 2.2 MeV M

_Z0

b

− M

B^∗B^∗

= 1.8 ± 1.7 MeV

-10 0 10 -10 0 10 -10 0 10

Υ(1S)π⁺π^- Υ(2S)π⁺π^- Υ(3S)π⁺π^- h_b(1P)π⁺π^- h_b(2P)π⁺π^- Average

Z_b(10610)

ΔM, MeV ΔΓ, MeV

Z_b(10650)

ΔM, MeV ΔΓ, MeV -10 0 10

FIG. 6: Comparison ofZb(10610) andZb(10650) parameters obtained from different decay channels. The vertical dotted lines indicateB^∗BandB^∗B^∗thresholds.

channelsB^∗B(10604.6 MeV/c²) andB^∗B^∗(10650.2 MeV/c²) that indicates “molecular” nature of these states and might explain most of the observed properties [16]. Preliminary announcement of these results triggered intensive discussion of other possible interpretations [17–20].

TABLE V: Comparison ofZb(10610) andZb(10650) parameters obtained from Υ(10860)→Υ(nS)π⁺π⁻ (n= 1,2,3) and Υ(10860)→hb(mP)π⁺π⁻(m= 1,2) analyses.

Final state Υ(1S)π⁺π⁻ Υ(2S)π⁺π⁻ Υ(3S)π⁺π⁻ hb(1P)π⁺π⁻hb(2P)π⁺π⁻ M(Zb(10610)), MeV/c² 10611±4±3 10609±2±3 10608±2±3 10605±2⁺³₋₁ 10596±7⁺⁵₋₁ Γ(Zb(10610)), MeV/c² 22.3±7.7^+3.0₋_4.0 24.2±3.1^+2.0₋_3.0 17.6±3.0±3.0 11.4^+4.5+2.1₋_3.9₋_1.2 16⁺¹⁶⁺⁹₋₁₀₋₄ M(Zb(10650)), MeV/c² 10657±6±3 10651±2±3 10652±1±2 10655±3⁺¹₋210651±4⁺¹₋2

Γ(Zb(10650)), MeV/c² 16.3±9.8^+6.0₋2.0 13.3±3.3^+4.0₋3.0 8.4±2.0±2.0 20.9^+5.4+2.1₋4.7−5.7 12⁺¹¹⁺⁷₋9−2

Rel. normalization 0.57±0.21^+0.19₋_0.040.86±0.11^+0.04₋_0.100.96±0.14^+0.08₋_0.05 1.8^+1.0+0.1₋_0.7₋_0.5 1.3^+3.1+0.4₋_1.1₋_0.7 Rel. phase, degrees 58±43⁺⁴₋9 −13±13⁺¹⁷₋8 −9±19⁺¹¹₋26 188⁺⁴⁴⁺⁴₋58−9 256⁺⁵⁶⁺¹¹₋72−184

VI. ACKNOWLEDGEMENT

We thank the KEKB group for excellent operation of the accelerator, the KEK cryogenics group for efficient solenoid operations, and the KEK computer group and the NII for valuable computing and SINET3 network support. We acknowledge support from MEXT, JSPS and Nagoya’s TLPRC (Japan); ARC and DIISR (Australia); NSFC (China); MSMT (Czechia); DST (India); MEST, NRF, NSDC of KISTI, and WCU (Korea); MNiSW (Poland); MES and RFAAE (Russia); ARRS (Slovenia); SNSF (Switzerland); NSC and MOE (Taiwan); and DOE and NSF (USA).

[1] N. Brambillaet al., Eur. Phys. J. C71, 1534 (2011).

[2] K.-F. Chenet al.(Belle Collaboration), Phys. Rev. Lett.100, 112001 (2008).

Z Z’

B B B B

• Angular analysis → both state J

^P

= 1

⁺

• Proximity to thresholds favors molecule over tetraquark Z

b

∼ | BB

^∗

i = | ↑↑ + ↑↓i &

S − wave h

_b

(mP)π not suppressed Z

_b⁰

∼ | B

^∗

B

^∗

i = | ↑↑ − ↑↓i %

• Phase btw Z

_b

and Z

_b⁰

amplitudes is ∼ 0

^◦

for Υ(nS )ππ and

∼ 180

^◦

for h

b

(mP )ππ

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Υ(5 S ) → BB π, BB ^∗ π, B ^∗ B ^∗ π

= Molecule?

Total branching fraction:

sidebands Data

signal 2-body decays

Belle preliminary Belle preliminary

Data

One charged pion and

full reconstruction of one B meson:

[arXiv:1209:6450]

Preliminary

M(B)[GeV/c^�]

= Molecule?

Total branching fraction:

sidebands Data

signal 2-body decays

Belle preliminary Belle preliminary

Data

One charged pion and

full reconstruction of one B meson:

[arXiv:1209:6450]

Preliminary

P(B)[GeV/c]

• Preliminary study of Belle [arXiv:1209:6450]

• One charged pion and full reconstruction of one B B

⁺

→ J /ψK

⁺

→ D

⁰

π

⁺

B

⁺

→ J /ψK

^∗⁰

→ D

⁻

π

⁺

→ D

^∗−

π

⁺

• Total branching fraction 1 × 10

⁻⁴

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Summary of Υ(5 S ) → BBπ, BB ^∗ π, B ^∗ B ^∗ π

Results

• Recoil mass of the Bπ system:

M

_r

(Bπ) = q

E

_Υ(5S)²

− P (Bπ)

²

• Shape of combinatorial background estimated from wrong-sign Bπ combinations in data

Preliminary BB

B B

0 20 40 60 80 100 120

5 5.1 5.2 5.3 5.4 5.5

rM(Bπ)+M(B)- M_B, GeV/c²

Nevents/5 MeV/c2 (c)

}

MB MB=�� MeV

Mr(B ) +M(B) MB[GeV/c^�]

B r

Υ(5S) → B

^(∗)

B

^(∗)

π

Belle 121 fb

⁻¹

significance BB < 0.60% at 90% C.L.

BB

^∗

+ BB

^∗

4.25 ± 0.44 ± 0.69% 9.3σ B

^∗

B

^∗

+ B

^∗

B

^∗

2.12 ± 0.29 ± 0.36% 5.7σ

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Interpretation as Z _b → B ⁽ ^∗ ⁾ B ⁽ ^∗ ⁾ ?

Fit function

f = (M

r

(π))

Bkg + A

Z_b

+ A

_Z0

b

+ A

NR

BB

^∗

π B

^∗

B

^∗

π

Preliminary Preliminary

Mr( )[GeV] Mr( )[GeV]

Can be described by two models:

A

_Z_b

+ A

_Z0

b

or A

_Z_b

+ A

_NR

Significance of Z

b

→ BB

^∗

> 8σ

Well described by:

A

_Z0 b

or A

_Z0

b

+ A

_NR

Significance of Z

_b⁰

→ B

^∗

B

^∗

> 6.8σ

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Observation of Z _b → B ⁽ ^∗ ⁾ B ⁽ ^∗ ⁾

arXiv:1209.6450

Channel Fraction, %

Z

_b

Z

_b⁰

Υ(1S)π

⁺

0.32 ± 0.09 0.24 ± 0.07 Υ(2S )π

⁺

4.38 ± 1.21 2.40 ± 0.63 Υ(3S )π

⁺

2.15 ± 0.56 1.64 ± 0.40 h

_b

(1P )π

⁺

2.81 ± 1.10 7.43 ± 2.70 h

_b

(2P)π

⁺

4.34 ± 2.07 14.8 ± 6.22 B

⁺

B

^∗⁰

+ B

⁰

B

^∗⁺

86.0 ± 3.6 − B

^∗⁺

B

^∗⁰

− 73.4 ± 7.0

• B r (Z

_b⁰

→ BB

^∗

) insignificant

• If included, other fraction of Z

_b⁰

are reduced by 1.33

• Z

_b⁰

→ BB

^∗

suppressed w.r.t. B

^∗

B

^∗

despite much larger PHSP

Explanation

Molecule → admixture of BB

^∗

in Z

_b⁰

is small Challenging for tetraquark!

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First observation of Υ(5 S ) → Υ( nS )π ⁰ π ⁰

0 10 20 30 40 50 60

9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 M_miss(π⁰π⁰), GeV/c²

Events/ 10 MeV/c2

(b)

0 10 20 30 40 50 60

9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 M_miss(π⁰π⁰), GeV/c²

(a)

0 2 4 6 8 10 12 14 16 18 20

9.9 10 10.1 10.2 10.3 10.4

M(Υπ⁺π⁻), GeV/c²

(c)

(�S) (�S)

(�S)

re�ection e⁺e ^{� �}

µ⁺µ ^{� �} (�S) ⁺ ^{� �}

• First observation [arxiv:1207.4345]

B (Υ(5 S ) → Υ(1 S)π

⁰

π

⁰

) = (2.25 ± 0.11 ± 0.20) × 10

⁻³

B (Υ(5 S) → Υ(2 S)π

⁰

π

⁰

) = (3.79 ± 0.24 ± 0.47) × 10

⁻³

B (Υ(5 S ) → Υ(3 S )π

⁰

π

⁰

) = (2.09 ± 0.51 ± 0.34) × 10

⁻³

NEW In agreement with isospin relations cf.

B Υ(5S)→Υ(1S)π⁺π⁻

= (4.45±0.16±0.35)×10⁻³ B Υ(5S)→Υ(2S)π⁺π⁻

= (7.97±0.31±0.96)×10⁻³ B Υ(5S)→Υ(3S)π⁺π⁻ = (2.28±0.19±0.36)×10⁻³

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Dalitz analysis of Υ(5 S ) → Υ( nS )π ⁰ π ⁰

Analysis procedure is the same as for charged pions

S(s1,s2) =A(Z_b1) +A(Z_b2) +A(f₀(980)) +A(f₂(1275)) +C₁^NR+C₂^NRm²(ππ)

0 10 20 30

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 M(Y(1S) )max, (GeV/c²)

(Events/20 MeV/c2) ^(a)(�S) ^{� �}

0 10 20 30 40 50 60

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

M(π⁰π⁰), (GeV/c²)

(Events/50 MeV/c2) ^(b)

0 5 10 15 20 25 30 35

10.4 10.45 10.5 10.55 10.6 10.65 10.7 10.75 M(Y(2S) )max, (GeV/c²)

(Events/10 MeV/c2) ^(a)(�S) ^{� �}

w/Z^{( )}_b

w/oZ^{( )}_b

0 10 20 30 40

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

M(π⁰π⁰), (GeV/c²)

(Events/10 MeV/c2) ^(b)

0 10 20 30

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 M(Y(1S)π)max, (GeV/c²)

(Events/20 MeV/c2) ^(a)

0 10 20 30 40 50 60

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

M(π⁰π⁰), (GeV/c²)

(Events/50 MeV/c2) ^(b)

0 10 20 30

9.5 9.6 9.7 9.8 9.9 10 10.1 10.2

M(Y(1S)π)min, (GeV/c²)

(Events/20 MeV/c2) ^(c)

FIG. 3. Comparison of the fit results (open histograms) with experimental data (points with error bars) for Υ(1S)π⁰π⁰events in the signal region. Red and blue open histograms show the fit with and withoutZ⁰b’s, respectively. Hatched histograms show the background components.

0 5 10 15 20 25 30 35

10.4 10.45 10.5 10.55 10.6 10.65 10.7 10.75 M(Y(2S)π)max, (GeV/c²)

(Events/10 MeV/c2) ^(a)

0 10 20 30 40

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

M(π⁰π⁰), (GeV/c²)

(Events/10 MeV/c2) ^(b)

0 5 10 15 20 25 30 35

10.1 10.2 10.3 10.4 10.5

(Events/10 MeV/c2) ^(c)

FIG. 4. Comparison of the fit results (open histograms) with experimental data (points with error bars) for Υ(2S)π⁰π⁰events in the signal region. Red and blue open histograms show the fit with and withoutZb⁰’s, respectively. Solution A is shown.

Both solutions give non-distinguishable plots. Hatched histograms show the background components.

0 6 12 18

10.58 10.6 10.62 10.64 10.66 10.68 10.7 10.72 10.74 M(Y(3S)π⁰)_max, (GeV/c²)

(Events/4 MeV/c2) ^(a)

0 6 12 18

0.25 0.3 0.35 0.4 0.45 0.5 0.55

M(π⁰π⁰), (GeV/c²)

(Events/10 MeV/c2) ^(b)

0 6 12 18

10.48 10.5 10.52 10.54 10.56 10.58 10.6 10.62 10.64 M(Y(3S)π⁰)_min, (GeV/c²)

(Events/4 MeV/c2) ^(c)

TABLE V. Summary of results on fractions of individual channels in Υ(nS)π⁰π⁰final state.

Fractions, % Υ(1S) Υ(2S) solution A Υ(2S) solution B Υ(3S)

Z⁰_b(10610) 0.9^+2.2+0.5_−0.9−0.3(<4.6) 13.5^+6.8+3.2_−2.7−4.4 25.4^+6.2+4.2_−5.9−11 84⁺¹⁷⁺¹⁴₋₂₃₋₁₁ Z⁰_b(10650) 0.6^+2.5+0.5_−0.6−0.3(<4.8) 2.7^+3.0+1.5_−1.4−1.2(<8.0) 2.7^+5.8+1.2_−1.6−1.2(<12.4) 4.3^+2.4+3.5_−2.2−1.9(<10.9) f2(1275) 26.3±4.2^+7.8_−4.5 3.9^+3.4+3.8_−2.0−2.1 8.7^+4.6+3.9_−2.0−4.5 — Total S-wave 72.4±4.7^+5.6_−3.4 95.5^+5.2+6.0_−6.2−6.5 110⁺⁷⁺⁶₋₉₋₁₈ 65⁺¹²⁺¹⁸₋₁₅₋₁₇

Sum 100 116 145 153

(�S) ^{� �}

0 10 20 30

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 M(Y(1S)π)_max, (GeV/c²)

(Events/20 MeV/c2) ^(a)

0 10 20 30 40 50 60

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

M(π⁰π⁰), (GeV/c²)

(Events/50 MeV/c2) ^(b)

0 10 20 30

9.5 9.6 9.7 9.8 9.9 10 10.1 10.2

M(Y(1S)π)_min, (GeV/c²)

(Events/20 MeV/c2) ^(c)

0 5 10 15 20 25 30 35

10.4 10.45 10.5 10.55 10.6 10.65 10.7 10.75 M(Y(2S)π)max, (GeV/c²)

(Events/10 MeV/c2) ^(a)

0 10 20 30 40

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

M(π⁰π⁰), (GeV/c²)

(Events/10 MeV/c2) ^(b)

0 5 10 15 20 25 30 35

10.1 10.2 10.3 10.4 10.5

(Events/10 MeV/c2) ^(c)

FIG. 4. Comparison of the fit results (open histograms) with experimental data (points with error bars) for Υ(2S)π⁰π⁰events in the signal region. Red and blue open histograms show the fit with and withoutZ⁰_b’s, respectively. Solution A is shown.

Both solutions give non-distinguishable plots. Hatched histograms show the background components.

0 6 12 18

10.58 10.6 10.62 10.64 10.66 10.68 10.7 10.72 10.74 M(Y(3S)π⁰)_max, (GeV/c²)

(Events/4 MeV/c2) ^(a)

0 6 12 18

0.25 0.3 0.35 0.4 0.45 0.5 0.55

M(π⁰π⁰), (GeV/c²)

(Events/10 MeV/c2) ^(b)

0 6 12 18

10.48 10.5 10.52 10.54 10.56 10.58 10.6 10.62 10.64 M(Y(3S)π⁰)_min, (GeV/c²)

(Events/4 MeV/c2) ^(c)

TABLE V. Summary of results on fractions of individual channels in Υ(nS)π⁰π⁰final state.

Fractions, % Υ(1S) Υ(2S) solution A Υ(2S) solution B Υ(3S)

Z⁰b(10610) 0.9^+2.2+0.5_−0.9−0.3(<4.6) 13.5^+6.8+3.2_−2.7−4.4 25.4^+6.2+4.2_−5.9−11 84⁺¹⁷⁺¹⁴₋₂₃₋₁₁ Z⁰_b(10650) 0.6^+2.5+0.5_−0.6−0.3(<4.8) 2.7^+3.0+1.5_−1.4−1.2(<8.0) 2.7^+5.8+1.2_−1.6−1.2(<12.4) 4.3^+2.4+3.5_−2.2−1.9(<10.9) f2(1275) 26.3±4.2^+7.8_−4.5 3.9^+3.4+3.8_−2.0−2.1 8.7^+4.6+3.9_−2.0−4.5 — Total S-wave 72.4±4.7^+5.6_−3.4 95.5^+5.2+6.0_−6.2−6.5 110⁺⁷⁺⁶₋₉₋₁₈ 65⁺¹²⁺¹⁸₋₁₅₋₁₇

Sum 100 116 145 153

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(18)

Results of Dalitz plot analysis

Fit fractions

State Υ(1S) Υ(1S) Υ(3S)

solution A solution B

Z

_b⁰

< 3.5 13.5 ± 4.0 ± 1.8 30.0 ± 6.1 ± 3.6 44 ± 11 ± 3 Z

_b⁰⁰

< 3.5 < 7 < 13 4.2 at 90% C.L.

Cf. [arxiv:1207.4345]

Z

_b⁺

2.54

^+0.87−0.75

19.6

^+4.0−3.2

26.8

^+6.8_−4.2

Z

_b⁰⁺

1.04

^+0.65−0.33

5.8

^+1.5_−1.8

11.0

^+4.3−2.4

• Fit fractions of neutral and charged Z

b

s are consistent Υ(2 S )π

⁰

π

⁰

Υ(3 S )π

⁰

π

⁰

Combined

Significance of Z

_b

4.9σ 4.3σ 6.5σ

• No significant signal found in Υ(1 S )π

⁰

π

⁰

, but existence not excluded

• Υ(nS)π

⁰

π

⁰

channels are consistent with Z

_b

states being isotriplets

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Mini-Worskshop Bled 2013, Looking into Hadrons 9 July 2013

Marko Pet!č