Spectroscopy at LHCb
Paolo Gandini

INFN - Sezione di Milano
On behalf of the LHCb collaboration

September, 6-10th 2021

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Outline• This is very short talk → I will only cover just a set of recent results• The LHCb experiment is an extraordinary gym for spectroscopy both for “conventional” SM and “exotic”• LHCb offers excellent tracking, PID and trigger ef iciency + bene it from high cross-sections at LHC• Shopping list:
Paper in Preparation• Observation of a new T state• Evidence for a new structure in the J/ψp(p) systems in B → J/ψpp decays arXiv:2108.04720
Paper in Preparation• Observation of two new excited Ξ states decaying to Λ K π• Observation of excited Ω baryons in Ω → Ξ K π decays
arXiv:2107.03419+

Paolo Gandini

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Lomonosov 2021
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Observation of a new Tcc+ state• Presented at EPS-HEP for the irst time
• Double heavy spectroscopy is now a fact in the LHCb physics program!
• Charged state with double charm content (two D meson with same “charge” in the same inal state)• Very narrow peak just above the threshold with striking signi icance over background

Paper in Preparatio
LHCb-PAPER-2021-031

A lot of hype generated!

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Lomonosov 2021
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Observation of a new Tcc+ state• T , with a new quark content ccud
• Charged double-charmed state is manifestly exotic• Narrow peak in the D D π meson mass spectrum• The new state is just below D* D mass threshold• Sample is extremely pure
• Subtract fake-D background using 2D it to (m , m )• No evidence in opposite sign sample+cc0

Paper in Preparatio
LHCb-PAPER-2021-031

0 ++0Kπ

Kπ

DeltaM wrt the threshold

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Observation of a new Tcc+ state• This search nicely complements previous studies on states with double heavy quark content• E.g. in July 2020, LHCb announced the possible discovery of a four-charm quark tetraquark in J/ΨJ/Ψ
Phys. Rev. Lett. 119, 112001 (2017)

Science Bulletin 2020 65(23)1983-1993• Also new searches ongoing on other states in the available dataset• No signal is found and Upper Limits are set on the relevant mass window
arXiv:2105.06841
arXiv:2104.04759

Paolo Gandini

Lomonosov 2021

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New structure in J/ψp: Bs0→J/ψpp decays• New analysis involving pentaquark searches• LHCb has investigated many modes in the past involving the J/ψp system (but in baryons)• This analysis: amplitude analysis of flavour-untagged B →J/ψpp• Decay observed and reported by LHCb in 2019 → now amplitude analysis• Very interesting inal state because of the symmetry of the Dalitz plot• Sample of 797 ± 31 signal events
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Paolo Gandini

arXiv:2108.04720
NEW posted onarXiv last week0

Lomonosov 2021

J/ψpJ/ψp6

New structure in J/ψp: Bs0→J/ψpp decays• Evidence for a new structure in the J/ψp and J/ψp systems• Signi icance in the range of 3.1σ to 3.7σ, depending on the assigned J hypothesis• There could be even a “glueball” contribution in pp, but nothing signi icant is foundP

arXiv:2108.04720
NEW posted onarXiv last week

Bs0→J/ψpp7

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Observation of two new excited Ξb0 states decaying to Λb0 K− π+• New b-hadron resonances are being observed by the LHCb experiment• Thanks to the very abundant samples of Λ saved on disk
• Use both:b•Λ →Λ π•Λ →Λ π π πbcbc

Paper in Preparatio
LHCb-PAPER-2021-025-+-

Preliminary

Preliminary• Two narrow peaks in the Λ K- π+ mass spectrum are observedbPreliminary

nPaolo Gandini

WS sample

Lomonosov 2021

Preliminary

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Observation of two new excited Ξb0 states decaying to Λb0 K− π+• The states are consistent with the theoretical predictions to the 1D excited Ξ doublets
0bPreliminary

Paper in Preparatio
LHCb-PAPER-2021-025

Preliminary

WS sample

Con irmed decay patterns of the two peaks via intermediate resonances

Preliminarynf

Paolo Gandini

Lomonosov 2021

Preliminary

9Observation of excited Ωc0 baryons in Ωb-→ Ξc+ K- π− decays• New mode considered, irst observation• Four excited Ωc baryons are observed in the Ξ K mass projection• Their relative production rates, masses and natural widths are measured• Precise mass measurementc+arXiv:2107.03419-More than theactual control mode!

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Observation of excited Ωc0 baryons in Ωb− → Ξc+ K- π− decays• Project the Dalitz plot to see the intermediate resonances

arXiv:2107.03419

Comparison wrt the inclusive observation
Phys. Rev. Lett. 118, 182001 (2017)

Paolo Gandini

Lomonosov 2021

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Conclusions
This summer → 3 more hadrons have been added to the lisGrowing extremely fast!

https://www.nikhef.nl/~pkoppenb/particles.html• This was a very short talk containing only the very latest results• All results exploiting the large dataset collected during Run1 and Run2
• More research is ongoing + Upgrade effort speeding up• A bright future ahead for both conventional and exotica when more data will be available

Please stay tuned!
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