Beyond (4S)
November 09, 2020

A. Bondar (BINP), B. Fulsom (PNNL),
A. Gaz (Nagoya), R. Mizuk (LPI),
U. Tamponi (INFN Torino), K. Trabelsi (IJCLab)

Belle II General MeetingIntroduction• History▪ Under discussion since ~2014: Belle II Physics Book, Phase 2, …
▪ Feb 2020: Task Force requested by Executive Board to investigate options andadvantages of non-(4S) energies▪ Opportunity for unique physics with small luminosity• Possible Proposals▪ ~10 fb-1 @ near 10.75 GeV▪ ~30 fb-1 @ (6S) (~11 GeV), +100 fb-1 follow-up and >11 GeV?
▪ (4S)-(5S) Scan: ~1 fb-1 steps of ~20 MeV▪ Lower energies: >100 fb-1 @ (3S, …)• Factors: beam energy, luminosity, physics
Beyond (4S) / B2GM / 2020.11.09

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Physics Overview

33fb-1121fb-1

1.1ab-1~5fb-1~1fb-1~7fb-1
5pb-1• In-depth references▪ Bondar, Mizuk and Voloshin, “Bottomonium-like states: Physics case for energy scan above BB threshold at Belle-II”,
Mod. Phys. Lett. A 32, 1750025 (2017)▪ E. Kou et al., “The Belle II Physics Book”, Prog. Theor. Exp. Phys. 2019 123C01 (2019)
Beyond (4S) / B2GM / 2020.11.09

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Reminder: (5S) at Belle

121 fb-1• High-rate (5S) dipion transitions led to discovery of hb, hb, Zb(10610, 10650)
Zb(10610/50)
hb(2P)
hb(1P)

PRL 108, 032001 (2012)
PRL 108, 122001 (2012)
PRL 109, 232002 (2012)~200 citations>500 citations~100 citations

hb(2S)

Beyond (4S) / B2GM / 2020.11.09

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Zb(106XX)→phb(1P)

Motivation: (6S)• Belle limited by statistics• <1 fb-1 per scan point~4.6 fb-1• Not on s peak, Leff=~3 fb-1
PRL 117 142001 (2016)• (6S) → p+p- X▪ hb : evidence for Zb▪ (pS) exclusive: unpublished(5S)→pZb(10610/50)→pp(2S)
(6S)→pZb(10610)→pp(2S) only?

• Pending questions:▪ Zb: how many states, neutral partners?
▪ Is (6S) quarkonium or a four-quark state?
▪ Potential pathway to other bottomonium states
Beyond (4S) / B2GM / 2020.11.09

Belle Internal (2014)5

~1 fb-1

Motivation: “Yb(10750)”• Recent Belle analysis of p+p-(ll) transitions

(6S)

Yb(?)

(5S)

JHEP 10 (2019) 220• Observation of enhancement @ 10.75 GeV• Decays similar to (56S)→p+p-(123S)▪ Could there be a Zb enhancement?
▪ Could it be (3D) bottomonium or a tetraquark?
▪ Near B(*)B*p threshold regions
Wang, CPC 43, 123102 (2019)
Ali et al., PLB 802, 135217 (2020)
Bicudo, Cardoso & Wagner, arXiv:2008.05605 (2020)
Chen, Zhang & He, PRD 101, 014020 (2020)
Giron & Lebed, PRD 102, 014036 (2020)
Li et al., EPJC 80, 59 (2020)
Liang, Ikeno & Oset, PLB 803, 135340 (2020)…
Beyond (4S) / B2GM / 2020.11.09

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Analysis Preparations (Preliminary)• Yb(10750), (6S) MC sensitivity studies:• Proof of principle:

Inclusive and exclusive p+p-bb

(234S)→p+p-(1S)(mm) in Belle II data

Yb→p+p-(1S)
Signal MCFeb 2020 B2GM

Oct 2020 B2GM

Yb BkdMC:10fb-1

Data:
71 fb-1• Underway: h bottomonium transitions in early Belle II data

• Bottomonium Working Group meetings: every 2nd Friday
Beyond (4S) / B2GM / 2020.11.09

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Some Accelerator Considerations• Above (4S) Task Force input from SuperKEKB colleagues• Ongoing linac RF upgrade▪ Improve operational stability▪ Might reach energies up to ~11.26 GeV• (6S) / 11 GeV▪ Potentially possible (linac) in 2021
▪ Situation better after shutdown?

• Yb / 10.75 GeV▪ Possible (linac) in 2021
▪ Tuning/stability/luminosity TBD• Further discussion needed, see other talks today
Beyond (4S) / B2GM / 2020.11.09

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Conclusion• Task Force studying near-term plans for above (4S) data collection• Information available in BELLE2-NOTE-PH-2020-066• Useful initial dataset size O(10 fb-1) at ~10.75 GeV and O(30 fb-1) at ~11 GeV• Long list of potential analyses▪ (6S/b) → ppX inclusive▪ (6S/b) → pp(pS) exclusive▪ Also popo modes▪ (6S) → gWb → w(1S)▪ (6S/b) → g cb exclusive▪ (6S/b) → g X inclusive▪ (6S/b) → hX inclusive▪ (6S/b) → h(pS) exclusive▪ (6S/b) → h’(pS) exclusive▪ (6S/b) → wX exclusive▪ (6S) → fcb(1P) exclusive▪ (6S/b) → BB

▪ …probably more…

▪ Each represents a publication unique to Belle II• Potential to increase our physics output…hopefully we can make it possible!
Beyond (4S) / B2GM / 2020.11.09

9Thank you10