1 / 20

Unraveling the pattern of XYZ mesons. Phys. Lett. B 736 , 325 (201 4 )

Explore the origin and nature of XYZ mesons, discussing experimental findings, four-quark states, and meson-meson interactions. Investigate the challenges in identifying these resonances and implications for theory.

kharris
Download Presentation

Unraveling the pattern of XYZ mesons. Phys. Lett. B 736 , 325 (201 4 )

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hadron 2015 Virginia, USA Jefferson Lab On the origin of the XYZ mesons Unraveling the pattern of XYZ mesons. Phys. Lett. B 736, 325 (2014) Phys.Rev.Lett.103, 222001 (2009); Phys. Rev. D 79, 074010 (2009); Phys.Lett.B699, 291 (2011); Phys. Rev. D 76, 094022 (2007); Phys.Lett.B 709, 358 (2012) A. Valcarce (Univ. Salamanca) J. Vijande (Univ. Valencia)

  2. 1.- Introduction: Experiment vs. Theory Experiment: The november revolution (1974) Theory & Experiment: A quiet period (1974-2003) Experiment: The beginning of a new era (2003) 2.- Methodology Solving the four-quark problem 3.- Results for four-quark states Non-exotic states: Charmonium Exotic states: Predictions 4.- Looking for molecules Non-exotic states: Charmonium Exotic states: Completeness of quark-model calculations 5.- Too many X’s, Y’s and Z’s? 6.- Unraveling the pattern of XYZ mesons ... and beyond 7.- Conclusions Outline

  3. SLAC M = 3.695 GeV  = 2.7 MeV Experiment: The november revolution (1974) M = 3.105 GeV  < 1.3 MeV BNL M = 3.1 GeV   0 MeV SLAC Introduction

  4. Theory Introduction

  5. T. Barnes et al., Phys. Rev. D72, 054026 (2005) S. Godfrey and N. Isgur, Phys. Rev. D32, 189 (1985) Theory & Experiment: A quiet period (1974-2003) Central potential: Spin-spin interaction: Spin-orbit interaction: Introduction

  6. X(3872) <2.3 MeV Ds1(2460), JP=1+,  < 3.5 MeV Experiment: The beginning of a new era (2003) Ds0*(2317), JP=0+, <3.8 MeV Introduction

  7. ccnn = 0 R.L. Jaffe, Phys. Rev. D15, 267 (1977) Y(4660) X(3940) D0(2308) X(4260) Y(3940) Z(3930) DsJ(2317) DsJ(2460) X(3872) Z(4430) DsJ(2860) X(4160) DsJ(2700) Z1(4040) DsJ(3040) Y(4350) Z2(4240) X(4008) …… Are all these resonances (if they really do exist!) four-quark states and/or meson-meson molecules? This is again a challenge for theory!! This is an experimental challenge!! Introduction

  8. 3 3 1 1 3 3 1 1 2 2 4 4 ccnn 2 2 1,2  Q 1,2  Q 3,4  n 3,4  n Identical quarks → Pauli C-parity is a good symmetry Solving the Schrödinger equation for a 4q system: VM and HH cncn Methodology

  9. System: ccnn. Model: BCN 4q energies Energías del sistema 4q M1M2 threshold • There are no non-exotic deeply four-quark bound states (compact) J.V., A.V. et al., Phys. Rev. D76, 094022 (2007) Results for four-quark states

  10. 4600 4500 4400 4300 • One compact state in the ccnn system (JP=1+) 4200 4100 4000 3900 3800 System: cncn. Model: CQC 4q energies M1M2 threshold ) V e M ( J.V., A.V., N.B., Phys. Rev. D79, 074010 (2009) E - - - - - - 0 1 2 0 1 2 0 1 2 0 1 2 + + + + + + 8 ( 2 ) ( 2 4 ) ( 3 0 ) ( 2 1 ) ( 2 1 ) ( 2 1 ) ( 2 8 ) ( 2 4 ) ( 3 0 ) ( 2 1 ) ( 2 1 ) ( 2 1 ) I = 0 I = 1 Results for four-quark states

  11. (I) (II) The meson-meson interacting potential is obtained from the same quark-quark interaction used in the HH and VM methods, by means of the adiabatic approximation. D D D D We study the consequences of allowing for the rearrangement of quarks (I) or not (II). c c n n DD  D*D* Molecular states, how to look for them? We solved the scattering of two-meson systems in a coupled-channel approach by means of the Lippmann-Schwinger equation, looking for attractive channels. Looking for molecules

  12. (II) DD* – J/  X(3872) Hidden flavor sector: Charmonium (I) DD* T. F.-C., A.V., J.V., Phys. Rev. Lett. 103, 222001 (2009) JPC(I)=1++(0) There are no charged partners of the X(3872) [diquark-antidiquark] Looking for molecules

  13. Formalisms based on meson-meson configurations and those considering explicitly four-quark states are equivalent if (and only if) a full basis is considered. Meson – Meson Four-quark states (I) PDD (II) PDD* PD*D* Explicit flavor sector: Exotics We have analyzed all positive parity channels until JP=2+ Only one channel is attractive: (I) JP = (0) 1+ (I) JP = (0) 1+ JP(I)=1+(0) (I) T.F.C., A.V., J.V., Phys. Lett. B 699, 291 (2011) Looking for molecules

  14. c c n c n n w J/ c n D D Too many X’s, Y’s and Z’s? T.F.C., A.V., J.V., Phys. Lett. B 709, 358 (2012) Too many X's, Y's and Z's?

  15.  aQn (Qn)(nQ) Unraveling the pattern of XYZ mesons (bnbn) (QnQn) L=0,S=1,C=+1,P=+1,I=0 (QQ)(nn) (Qn)(nQ) Central Spin-spin MQQ + Mnn MQn + MnQ (bnbn) L=0,S=1,C=+1,P=+1,I=1 (Qn)(nQ) (QQ)(nn) Hadron 2015 / A. Valcarce Unraveling the pattern of XYZ mesons... 15/19

  16. Reversed levels Normal ordering Degeneracy Continuum state Threshold Bound state L=0,S=1,C=+1,P=+1,I=0 =0  E[(Qn)(nQ)] = E[(QQ)(nn)] : Degeneracy >0  E[(Qn)(nQ)] > E[(QQ)(nn)] : Normal ordering <0  E[(Qn)(nQ)] < E[(QQ)(nn)] : Reversed levels X axis =E[(Qn)(nQ)] – E[(QQ)(nn)] =1  E[(QnQn)] = [E(M1)+E(M2)] : Threshold >1  E[(QnQn)] > [E(M1)+E(M2)] : Continuum state <1  E[(QnQn)] < [E(M1)+E(M2)] : Bound state Y axis EK=22[(QnQn)]/[E(M1)+E(M2)] Hadron 2015 / A. Valcarce 16/19 Unraveling the pattern of XYZ mesons...

  17. A possible example of this mechanism: Four quark systems Belle Collaboration c n P-wave pion exchange model  JP=1+ 1 0 S-wave 4482 MeV D(1S) D*(2S) n c D ~ 50 MeV 2S 1S 4433 MeV D*(1S) D(2S) D(1S) D*(2S)  D(1S) D*(2S)  VOPE = 0 D*(1S) D(2S)  D*(1S) D(2S)  VOPE = 0 D(1S) D*(2S)  D*(1S) D(2S)  VOPE ≠ 0 D D*   Forbidden Allowed D D T. Barnes, F.E. Close, E.S. Swanson Hadron 2015 / A. Valcarce ... and beyond 17/19

  18. Diquark hypothesis:Q nn (QnQn)  (Qnnnn) (Qnn)(nn) (nnn)(Qn) MQnn + Mnn Mnnn+ MQn Another possible example: Five quark systems BABAR Collaboration R.M. Albuquerque, S.H. Lee, M. Nielsen Hadron 2015 / A. Valcarce ... and beyond 18/19

  19. Conclusions • Increasing interest in hadronic spectroscopy due to the advent of a large number of experimental data of difficult explanation: XYZ mesons. • These data provide with the best laboratory for studying QCD in what N. Isgur called the strong limit. We have the methods, so we can learn about the dynamics. • Hidden flavor components (unquenching the quark model) offer a possible explanation of new experimental data and old problems in the meson and baryon spectra. There is not a proliferation of multiquarks, they are very rare. • We have presented a plausible mechanism explaining the origin of the XYZ mesons: When there is an attractive interaction characterizing the (Qn)(nQ) upper system combined with the vicinity of the two allowed thresholds, a four-quark bound state may emerge. • Experimentalists: Exotic charmed four-quark states may exist if our understanding of the low-energy QCD dynamics does not hide some important information. We do not find evidence for charged and bottom partners of the X(3872). To answer these questions is a keypoint to advance in the study of hadron spectroscopy. • Theorists: We have seen many different approaches to explain the new charmonium states. It would be great to extend these models to other sectors making predictions that may be tested in the near future. Conclusions 19/19

  20. There should not be a partner of the X(3872) in the bottom sector There should be a JP=1+ bound state in the exotic bottom sector Hidden flavor Explicit flavor Too many X's, Y's and Z's?

More Related