Hadron spectroscopy and exotic states at LHCb Tomasz

Hadron spectroscopy and exotic states at LHCb Tomasz Skwarnicki on behalf of the LHCb collaboration Moriond QCD March 26, 2019

2 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Run 1 + Run 2 9 fb-1 LHCb-PAPER-2019 -005 in preparation PLB 769, 187 (2017) PRL 96, 082003 (2006) PRD 81, 092003 (2010) Purely hadronic final states! preliminary First observation of hadroproduction of y(3770) (dominantly y(13 D 1) state) Likely y(13 D 3) state preliminary first observation Likely cc 2(23 P 2) state

3 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Status of charmonium spectroscopy cc 2(23 P 2) improved y(13 D 3) y(13 D 1) added ----- T. Barnes, S. Godfrey, and E. S. Swanson Phys. Rev. D 72, 054026 (2005): LHCb-PAPER-2019 -005 in preparation relativized NR small decay phase-space and L=3 centrifugal barrier! Masses of wide charmonium states are overestimated in potential approaches.

4 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 4 LHCb-PAPER-2019 -007 in preparation Run 1 + Run 2 8. 5 fb-1 S. Godfrey ----Phys. Rev. D 70, 054017 (2004) g (undetected) Confirm the recently presented CMS results arxiv: 1902. 00571 (see the talk by Greg Landsberg) (also ATLAS PRL 113 (2014) 12004; two peaks unresolved)

5 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Tightly-bound pentaquark PRL 115, 072001 (2015) Run 1 3 fb-1 Loosely-bound pentaquark • Decay by fall-apart: – – Amplitude model fit to masses and decay angles – • Wu, Molina, Oset, Zou, PRL 105 (2010) 232001 Wang, Huang, Zhang, Zou, PR C 84 (2011) 015203 Karliner, Rosner, PRL 115 (2015) 122001 and others Spectrum (confining potential) – Wide states? What slows it down to make Pc(4450)+ narrow? L between diaquarks? Pc(4380)+ S=1, L=0 broad, Pc(4450)+ S=0, L=1 narrow Many states expected (n, L, S) L. Maiani, A. D. Polosa, V. Riquer, PL B 749 (2015) 289 R. F. Lebed, PL, B 749 (2015) 454 V. V. Anisovich, M. A. Matveev, J. Nyiri, A. V. Sarantsev PL, . B 749 (2015) 454 and others Guo, Meissner, Wang, Yang, PRD 92 (2015) 071502

6 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 9 x more than used in the Run 1 2015 -2016 papers LHCb-PAPER-2019 -014 in preparation Run 1 + Run 2 9 fb-1 First presentation! 6. 4% background

7 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Data consistency check 6 D amplitude model fit to masses and decay angles • When fit with the 2015 amplitude model, the full data sample gives the Pc(4450)+ and Pc(4380)+ parameters consistent with the 2015 results • But…

8 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Coarse binning! LHCb-PAPER-2019 -014 in preparation Run 1 + Run 2 Fine binning! Run 1 + Run 2

9 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Pc(4440)+ Pc(4457)+ Pc(4312)+ Mass resolution s=2. 3 -2. 7 (FWHM 5. 4 -6. 4) Me. V LHCb-PAPER-2019 -014 in preparation Pc(4457)+ Pc(4440)+ Pc(4312)+ Proper amplitude analysis faces new challenges: must consider m. J/yp resolution effects, large statistics and sub-percent precision in fit fractions required in the amplitude model – work in progress

10 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 LHCb-PAPER-2019 -014 in preparation Three narrow Breit-Wigner resonances + high-order polynomial low-order polynomial + broad Pc+ as bkg. high m. Kp low m. Kp 7. 6 s 5. 4 s Different composition of L* reflections. Tests systematic uncertainties. (2 vs 1) Best statistical sensitivity Event weight-function The fitting approaches verified with large statistics 6 Damplitude-model simulations approximating the data, and ensemble of pseudoexperiments with the statistics matching the real data.

Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 11 Fits with interferences • Nominal fits preformed with incoherent sum of Breit-Wigner amplitudes. • Also perform fits with coherent sum between various Breit. Wigner amplitudes, including the broad Pc+ state (implies the same spin and parity). • No significant evidence for interferences, but the source of the largest systematic uncertainty on the mass and width determinations. Example of the fit with interference: Pc(4312)+ interfering with the broad Pc+ Before interference

Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 12 Results LHCb-PAPER-2019 -014 in preparation

13 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Plausible theoretical interpretation Predicted JP: The only thresholds below which molecular bound states are expected in this mass range LHCb-PAPER-2019 -014 in preparation

14 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Plausible theoretical interpretation Predicted JP: The only thresholds below which molecular bound states are expected in this mass range LHCb-PAPER-2019 -014 in preparation The near-threshold masses and the narrow widths of Pc(4312)+, Pc(4440)+ and Pc(4457)+ favor “molecular” pentaquarks with meson-baryon substructure! However, we need to measure JPs to confirm molecular hypothesis, find isospin partners, … Pc(4312)+, Pc(4440)+ not near triangle diagram thresholds, Pc(4457)+ is (see backup slides). Can diquark substructure separated by a potential barrier [Maiani, Polosa, Riquer, PL, B 778, 247 (2018)] produce width suppression? Are masses near thresholds just by coincidence? This hypothesis is not ruled out

15 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Comparison to numerical predictions • Example: ar. Xiv: 1202. 1036 PR C 85 044002 (2012) 4314. 5 Me. V L - cut off on exchanged meson mass.

Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 • Summary 16

Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 BACKUP SLIDES Maiani, Polosa, Riquer, PL, B 778, 247 (2018) 17

18 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Could the narrow Pc+ peaks be due to hadron rescattering via triangle diagrams? LHCb-PAPER-2019 -014 in preparation Pc(4312)+, Pc(4440)+ are too far from any rescattering thresholds to be triangle diagram peaks (see the next slide) triangle BW BW Amplitude analysis will have more handles on distinguishing trianglediagram and BW amplitudes

19 Moriond QCD, Tomasz Skwarnicki, Mar 26, 2019 Could the narrow Pc+ peaks be due to hadron rescattering via triangle diagrams? LHCb-PAPER-2019 -014 in preparation 3 triangle-diagram amplitudes + polynomial Pc(4312)+, Pc(4440)+ are too far from any rescattering thresholds to be triangle diagram peaks