Narrow Structures in High Statistics Diffractive Photoproduction

Narrow Structures in High Statistics Diffractive Photoproduction Simone Pacetti Università di Perugia and Laboratori Nazionali di Frascati Narrow Structures in High Statistics Diffractive Photoproduction p.1/18

Summary A narrow structure ( and ) observed by E687 in the pions final state data of the diffractive photoproduction and possible interpretations (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) Connection between photoproduction and Set of data and fit Properties of the dip Possible nature of the dip annihilation A new analysis of sub-structures in the pions final state of the E687 diffractive photoproduction (P. Lebrun Hadron 97, Aug. 25-30, 1997) Fit of the distribution Fit of the distribution Fit of the residual and parameters Narrow Structures in High Statistics Diffractive Photoproduction p.2/18

Summary A narrow structure ( and ) observed by E687 in the pions final state data of the diffractive photoproduction and possible interpretations (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) Connection between photoproduction and Set of data and fit Properties of the dip Possible nature of the dip annihilation A new analysis of sub-structures in the pions final state of the E687 diffractive photoproduction (P. Lebrun Hadron 97, Aug. 25-30, 1997) Fit of the distribution Fit of the distribution Fit of the residual and parameters Diffractive photoproduction data as source of information on the nature of the scalar meson Narrow Structures in High Statistics Diffractive Photoproduction p.2/18

Summary A narrow structure ( and ) observed by E687 in the pions final state data of the diffractive photoproduction and possible interpretations (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) Connection between photoproduction and Set of data and fit Properties of the dip Possible nature of the dip annihilation A new analysis of sub-structures in the pions final state of the E687 diffractive photoproduction (P. Lebrun Hadron 97, Aug. 25-30, 1997) Fit of the distribution Fit of the distribution Fit of the residual and parameters Diffractive photoproduction data as source of information on the nature of the scalar meson Conclusions Narrow Structures in High Statistics Diffractive Photoproduction p.2/18

Photoproduction and Annihilation Naive Vector Meson Dominance Narrow Structures in High Statistics Diffractive Photoproduction p.3/18

Photoproduction and Annihilation Naive Vector Meson Dominance should vary slowly with Since the cross section Narrow Structures in High Statistics Diffractive Photoproduction p.3/18

2 2 E687 data (P. Lebrun Hadron 97, Aug. 25-30, 1997) 2500 2000 Arbitrary Units 1500 1000 500 0 1 1.5 2 2.5 3 M(4π)(GeV/c 2 ) Narrow Structures in High Statistics Diffractive Photoproduction p.4/18

2 2 E687 weighted data compared to BaBar data (P. Lebrun Hadron 97, Aug. 25-30, 1997) 30 E687 E687 (1/M 2 ) 25 BaBar Arbitrary Units 20 15 10 5 0 1 1.5 2 2.5 3 M(4π)(GeV/c 2 ) Narrow Structures in High Statistics Diffractive Photoproduction p.5/18

Evidence of a narrow resonance decaying in 6 pions The E687 experiment observes a narrow dip with and (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) Narrow Structures in High Statistics Diffractive Photoproduction p.6/18

Evidence of a narrow resonance decaying in 6 pions The E687 experiment observes a narrow dip with and (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) The quantum numbers of this structure are, (6 pions) and. Narrow Structures in High Statistics Diffractive Photoproduction p.6/18

Evidence of a narrow resonance decaying in 6 pions The E687 experiment observes a narrow dip with and (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240) The quantum numbers of this structure are, (6 pions) and. This dip is similar to that observed by the DM2 coll. with lower statistics, in the channels and. Narrow Structures in High Statistics Diffractive Photoproduction p.6/18

DM2 data 2.5 (DM2 Fenice Workshop, Frascati, 1988) 2.0 1.5 1.0 0.5 0 1400 1600 1800 2000 2200 2400 Narrow Structures in High Statistics Diffractive Photoproduction p.7/18

New fit Jacob Slansky Arbitrary Units Arbitrary Units 120 100 80 60 40 20 [(Events/Acceptance)(M6π 2 ) -1 ](MeV/c 2 ) -1 120 100 80 60 40 20 [(Events/Acceptance)(M6π 2 ) -1 ](MeV/c 2 ) -1 1.6 1.8 2 2.2 2.4 M 6π (GeV) 0 0 1.6 1.8 2 2.2 2.4 2.6 2.8 3 M 6π (GeV) The data used are rescaled by the factor A Breit-Wigner is added in the fit function to account the interference with the Narrow Structures in High Statistics Diffractive Photoproduction p.8/18

New fit Jacob Slansky Arbitrary Units Arbitrary Units 120 100 80 60 40 20 [(Events/Acceptance)(M6π 2 ) -1 ](MeV/c 2 ) -1 120 100 80 60 40 20 [(Events/Acceptance)(M6π 2 ) -1 ](MeV/c 2 ) -1 1.6 1.8 2 2.2 2.4 M 6π (GeV) 0 0 1.6 1.8 2 2.2 2.4 2.6 2.8 3 M 6π (GeV) The data used are rescaled by the factor A Breit-Wigner is added in the fit function to account the interference with the The relative phase between the dip and the background amplifies the effect. Narrow Structures in High Statistics Diffractive Photoproduction p.8/18

+ 4 + * $ " $! ' 0 Fit results Phase Mass Width Resonances ) (Yield/10 MeV) (deg.) ) (MeV/c (GeV/c Phase Background (deg.) (fixed), - -/. <; 8:9 % 576 &) ( &'!#" %!#" 3 %21 The Breit-Wigner added to the fit function is compatible with the well known Narrow Structures in High Statistics Diffractive Photoproduction p.9/18

+ 4 + * $ " $ 3! ' 0 Fit results Phase Mass Width Resonances ) (Yield/10 MeV) (deg.) ) (MeV/c (GeV/c (PL B514 240) Phase Background (deg.) (fixed), - -/. <; 8:9 % 576 &) ( &'!#" %!#" %21 In this case interference only with real background The Breit-Wigner added to the fit function is compatible with the well known Narrow Structures in High Statistics Diffractive Photoproduction p.9/18

Mixing mechanism (P.J. Franzini-F.J. Gilman) Complex mass Narrow Structures in High Statistics Diffractive Photoproduction p.10/18

Mixing mechanism (P.J. Franzini-F.J. Gilman) Complex mass Coupling constant Narrow Structures in High Statistics Diffractive Photoproduction p.10/18

Mixing mechanism (P.J. Franzini-F.J. Gilman) Complex mass Coupling constant This mixing mechanism produces a cross-section with a dip structure independent of the nature of Narrow Structures in High Statistics Diffractive Photoproduction p.10/18

Not a Since the dip mass ( interpreted as a bound state ) is similar to bound state. this structure could be Narrow Structures in High Statistics Diffractive Photoproduction p.11/18

Not a Since the dip mass ( interpreted as a bound state ) is similar to bound state. this structure could be Recently the OBELIX experiment has looked for such a resonance in with a negative result. Phys. Lett. B527 (2002) 39. Trend expected in case of resonance at Narrow Structures in High Statistics Diffractive Photoproduction p.11/18

Not a Since the dip mass ( interpreted as a bound state ) is similar to bound state. this structure could be Recently the OBELIX experiment has looked for such a resonance in with a negative result. Phys. Lett. B527 (2002) 39. Narrow resonances, in agreement with a bound state, have been observed at not consistent with the E687 dip because of the mass difference. Trend expected in case of resonance at Narrow Structures in High Statistics Diffractive Photoproduction p.11/18

Possible nature of the dip. Hybrid? The resonance could be interpreted as a hybrid bound state. Narrow Structures in High Statistics Diffractive Photoproduction p.12/18

Possible nature of the dip. Hybrid? The resonance could be interpreted as a hybrid bound state. The Flux-tube model (Isgur-Paton) predicts the existence of new species of hadrons called hybrids, who have both quark and gluonic (excited color flux tube) degrees of freedom in evidence. Nonstrange hybrid mesons are predicted at Similar predictions come also from lattice calculations. (strange at ). These hybrids have small, but not vanishing, e.m. widths. The breaking mechanism of the strings forbids decay into identical mesons and imposes spin a parity of the products. Narrow Structures in High Statistics Diffractive Photoproduction p.12/18

Possible nature of the dip. Hybrid? The resonance could be interpreted as a hybrid bound state. The Flux-tube model (Isgur-Paton) predicts the existence of new species of hadrons called hybrids, who have both quark and gluonic (excited color flux tube) degrees of freedom in evidence. Nonstrange hybrid mesons are predicted at Similar predictions come also from lattice calculations. (strange at ). These hybrids have small, but not vanishing, e.m. widths. The breaking mechanism of the strings forbids decay into identical mesons and imposes spin a parity of the products. These selection rules in two-body decay, should favor high multiplicity channels and relative small widths (???). Narrow Structures in High Statistics Diffractive Photoproduction p.12/18

Fit and residual of E687 data (S.P. Ratti, HEP, Jerusalem, 19-26 Aug. 1997) 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 700 600 500 400 300 200 The high sensibility of the E687 experiment permits to detect clearly the interference. 100 0 100 200 300 400 500 600 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 Narrow Structures in High Statistics Diffractive Photoproduction p.13/18

Fit and residual of E687 data (S.P. Ratti, HEP, Jerusalem, 19-26 Aug. 1997) 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 700 600 500 400 300 200 The high sensibility of the E687 experiment permits to detect clearly the interference. 100 0 100 200 300 400 500 600 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 200 150 100 50 0 50 100 By subtracting the interference pattern the structure in the residual disappears. 150 200 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 Narrow Structures in High Statistics Diffractive Photoproduction p.13/18

Possible sub-structures in final state The E687 data seem to have fluctuating behaviors in some energy regions. 2500 2000 (P. Lebrun Hadron 97, Aug. 25-30, 1997) Arbitrary Units 1500 1000 500 0 1 1.5 2 2.5 3 M(4π)(GeV/c 2 ) Narrow Structures in High Statistics Diffractive Photoproduction p.14/18

Possible sub-structures in final state The E687 data seem to have fluctuating behaviors in some energy regions. 2500 2000 (P. Lebrun Hadron 97, Aug. 25-30, 1997) Arbitrary Units 1500 1000 500 0 1 1.5 2 2.5 3 M(4π)(GeV/c 2 ) We apply the same procedure of the 2 pions. Doing the fit Computing the residual If there are, fitting the structures Narrow Structures in High Statistics Diffractive Photoproduction p.14/18

New fit and residual of the rescaled data (P. Lebrun Hadron 97, Aug. 25-30, 1997) σ diff (nb) 30 25 Data and Fit 20 15 10 5 0 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 q(gev) Narrow Structures in High Statistics Diffractive Photoproduction p.15/18

New fit and residual of the rescaled data (P. Lebrun Hadron 97, Aug. 25-30, 1997) σ diff (nb) 30 25 Data and Fit σ diff - Dati (nb) 1.5 1 Fit Data 20 0.5 15 0 10-0.5 5-1 0 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 q(gev) -1.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 q(gev) Narrow Structures in High Statistics Diffractive Photoproduction p.15/18

Fit of the residual (P. Lebrun Hadron 97, Aug. 25-30, 1997) σ diff - Dati (nb) 1.5 1 0.5 0-0.5-1 -1.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 q(gev) Narrow Structures in High Statistics Diffractive Photoproduction p.16/18

Fit of the residual (P. Lebrun Hadron 97, Aug. 25-30, 1997) 1.5 1 - Dati (nb) σdiff 0.5 0-0.5-1 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 q(gev) -1.5 Resonances Narrow Structures in High Statistics Diffractive Photoproduction p.16/18

Conclusions The dip, found at by E687 (P.L. Frabetti et al. Phys. Lett. B514 (2001) 240), is investigated by means of a new fit function. Its nature appears consistent with a narrow resonance, strongly interfering with the vector meson. A resonance is unlikely according to the negative result of OBELIX (Phys. Lett. B527 (2002) 39). An interpretation of this resonance as an with expected mass, width and decay mode., isovector hybrid is in agreement We suggest the possible existence of some sub-structures in the E687 photoproduction data (P. Lebrun Hadron 97, Aug. 25-30, 1997). The interpretation of these structures in terms of resonances needs much more precise data. With a statistics one order of magnitude bigger, such as the one foreseen for DA NE2, the secrets of this rich energy region could be revealed. Narrow Structures in High Statistics Diffractive Photoproduction p.17/18