Quasi-free Cross Section Measurements at CLAS: D p - (p) D K + - - PowerPoint PPT Presentation

Hadron 2013 November 5, 2013

Paul Mattione, Carnegie Mellon University for the CLAS Collaboration supported by the DOE Office of Science

Quasi-free Cross Section Measurements at CLAS:

γD à pπ-(p) γD à K+Σ*(1385)-(p) γD à K*(892)0Λ(p)

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Outline

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Introduction to N*’s

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CLAS g13 experiment & analysis

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Differential cross section measurements

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γD à pπ-(p)

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γD à K*(892)0Λ(p) & γD à K+Σ*(1385)-(p)

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Comparison to ground state γp à K+Λ & γD à K+Σ-(p)

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Summary & conclusions

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Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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Introduction to N*’s

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

N* Resonance Spectrum (2012)

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[1, 2, 3]

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Predicted N* spectrum (Capstick, Isgur) [1]

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Quark model

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PDG [3] changes since 2010:

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4 new PDG resonances (vertical bars)

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2 states upgraded to ***: N(1900)[3/2]+, N(1875)[3/2]-

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Most searches:

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Proton targets, non-strange channels (e.g. πN)

Legend Black: “Established” (4*, 3*) [3] Blue: Inconclusive (2*, 1*) [3] Red: Unobserved [3]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Searching for N* Resonances

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Legend Black: “Established” (4*, 3*) [3] Blue: Inconclusive (2*, 1*) [3] Red: Unobserved [3] Cyan: γN à à K*(892)Λ [5]

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“Missing” N* resonances [1]

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Wide, overlapping

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Correlated quark-pair? [4]

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N* decays: KY, K*Y, KY*

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Couplings sizable vs. Nπ [3]

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Sparse γn data vs. γp

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Amplitudes (isospin)

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No known γn à K*(892)0Λ cross section measurements

[1, 2, 3]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Searching for N* Resonances

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Legend Black: “Established” (4*, 3*) [3] Blue: Inconclusive (2*, 1*) [3] Red: Unobserved [3] Violet: γN à à KΣ*(1385) [5]

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“Missing” N* resonances [1]

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Wide, overlapping

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Correlated quark-pair? [4]

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N* decays: KY, K*Y, KY*

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Couplings sizable vs. Nπ [3]

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Sparse γn data vs. γp

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Amplitudes (isospin)

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LEPS γn à K+Σ*(1385)- data limited to low-θ [6]

[1, 2, 3]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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CLAS g13 Experiment and Analysis

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

JLab: CEBAF, CLAS, & g13

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JLab CEBAF accelerator: up to 6 GeV e- [7]

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CLAS detector (Hall B) [8]

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DC: Tracking, TOF: Timing

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g13 experiment: 10/06 – 06/07, LD2 target

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Analysis: Ee- = 2.655 GeV, circularly polarized γ’s

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γ beam: radiator, γ tagger detects e- [9]

CLAS [8] CEBAF [7] γ Tagger [9]

→

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Event Selection

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γD à K*(892)0Λ(p) & γD à K+Σ*(1385)-(p)

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Final state: K+, π-, p ,π-, (p)

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Cuts: Λ, (p) masses

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γD à pπ- (p): Cut on (p) mass

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All: Select quasi-free events:

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Cut missing momentum > 200 MeV/c

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Still large rescattering effects for Eγ > 1 GeV, θ < ~ 15° - 30° [10]

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Λ (p)

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Dalitz Plots

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K*(892)0 à K+π-

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Yield: ~17000 K*(892)0Λ events, ~100000 K+Σ*(1385)- events

Color scale changes with row Cut Σ*- in K*0 analysis (dominates) Don’t cut K*0 in Σ*- analysis:

• Potential interference < systematics

Σ*(1385)- à Λπ-

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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Differential Cross Section Measurements

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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CLAS g13: Preliminary, high statistics: ~300 million events in ~9000 bins:

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10- & 20-MeV-wide bins from 0.56 < Eγ (GeV) < 2.52

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Significant increase in statistics: CLAS g10 [11] had ~3000 bins

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Compared to CLAS g10 [11], SAID CM12 [12], BnGa12-1 [13]

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Statistical uncertainties only (g10 pre-FSI correction)

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γD à pπ-(p) Cross Section

Legend Black: CLAS g13 Red: CLAS g10 [11] Blue: SAID CM12 [12] Green: BnGa12-1 [13]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γD à pπ-(p) Cross Section

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Overall good matching between g10 & g13, need more acceptance studies

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Data will improve:

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Understanding of N* couplings to neutron in πN

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Understanding of rescattering: working with Igor Strakovsky (GWU)

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Legend Black: CLAS g13 Red: CLAS g10 [11] Blue: SAID CM12 [12] Green: BnGa12-1 [13]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γD à K+Σ*(1385)-(p) Cross Section

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Data: LEPS [6], Preliminary CLAS g13, Oh et. al model [14]:

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CLAS g13: ~100000 events, no systematic errors, ~ -0.5 < cos(θ) < 0.75

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Oh, et. al model: Effective Lagrangians

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Dominated by t-channel K+ and K*+, some N*’s and Δ*’s included

Legend Black: CLAS g13 (preliminary) Red: LEPS [6] Blue: Oh, et. al Model [14]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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γD à K+Σ*(1385)-(p) Cross Section

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t-channel dominated

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g13 & LEPS close, model significantly lower

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Disagreement with prediction: perhaps t-channel modeling

Legend Black: CLAS g13 (preliminary) Red: LEPS [6] Blue: Oh, et. al Model [14]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γD à K*(892)0Λ(p) Cross Section

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Data: Preliminary CLAS g13 (~12000 events, no systematic errors)

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S.-H. Kim, et. al model [15]: Effective Lagrangians

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K0 t-channel exchange dominates, N[3/2-](2080) is dominant N*

Legend Black: CLAS g13 Red: Kim et. al w. N*’s [15] Blue: Kim et. al w/o N*’s [15]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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t-channel dominated

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Disagreement with prediction: perhaps t-channel modeling

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Possible small K*(892)0Σ0 background leakage, need to investigate

γD à K*(892)0Λ(p) Cross Section

Legend Black: CLAS g13 Red: Kim et. al w. N*’s [15] Blue: Kim et. al w/o N*’s [15]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γD à K*(892)0Λ(p) vs. γp à K+Λ

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~Comparison vs. ground state [16] (γD à K0Λ(p) being analyzed):

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Similar at Mid-θ

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Rescattering through πN: ~20% effect on KΛ [17]

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K*Λ sizable vs. KΛ: N* coupled-channels analyses

Legend Black: g13 γD à K*(892)0Λ(p) Red: CLAS g11 γp à K+Λ [16]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γD à K+Σ*(1385)-(p) vs. γD à K+Σ-(p)

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Scale comparison vs. ground state

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Similar scale in most regions

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KΣ*(1385): N* coupled-channels analyses

Legend Black: g13 γD à K+Σ*(1385)-(p) Red: LEPS γn à K+Σ*(1385)- [6] Blue: CLAS g10 γn à K+Σ- [18]

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

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Summary & Conclusions

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

Summary & Conclusions

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N* spectrum: Strong force and hadronic structure

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Role of quark correlations: limit N* spectrum

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Search in KY, K*Y, and KY* channels

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Preliminary quasi-free cross sections:

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γD à pπ-(p), γD à K*(892)0Λ(p), & γD à K+Σ*(1385)-(p)

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N* couplings, greater understanding of interactions

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High-statistics γD à pπ-(p) data: study rescattering

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K*Y & KY* sizable vs. KY: include in coupled-channels analyses

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These results will be published after systematic studies are performed, and will contribute to the search for the N* resonances.

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Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

References

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[1] S. Capstick and N. Isgur, Phys. Rev. D 34, 2809 (1986).

[2] W. Roberts, http://www.physics.fsu.edu/users/roberts/roberts_hadrons.html [3] K. Nakamura et al. (The Particle Data Group), J. Phys. G 37, 075021 (2010).

[4] E. Santopinto, Phys. Rev. C 72, 022201(R) (2005).

[5] S. Capstick and W. Roberts, Phys. Rev. D 58, 074011 (1998). [6] K. Hicks et al. (The LEPS Collaboration), arXiv:0812.0771 [nucl-ex] (2008). [7] C. W. Leemann, D.R. Douglas, G.A. Krafft, Annu. Rev. Nucl. Part. Sci. 51, 413 (2001). [8] B. A. Mecking et al. (The CLAS Collaboration), Nucl. Instr. and Meth. A 503, 513 (2003). [9] D. I. Sober et al. (The CLAS Collaboration), Nucl. Instr. and Meth. A 440, 263 (2000). [10] V. E. Tarasov et al., Phys. Rev. C 84, 035203 (2011). [11] W. Chen et al. (The CLAS Collaboration), Phys. Rev. Lett. 103, 012301 (2009). [12] CNS DAC Services (SAID Program), http://gwdac.phys.gwu.edu/ [13] Bonn Gatchina Partial Wave Analysis, http://pwa.hiskp.uni-bonn.de/ [14] Y. Oh, C. M. Ko, K. Nakayama, Phys. Rev. C 77, 045204 (2008).

[15] S.-H. Kim, S.-i. Nam, Y. Oh, H.-C. Kim, Phys. Rev. D 84, 114023 (2011).

[16] M. E. McCracken et al. (The CLAS Collaboration), Phys. Rev. C 81, 025201 (2010). [17] W-T. Chiang, F. Tabakin, T.-S. H. Lee, and B. Saghai, Phys. Lett. B 517, 101 (2001). [18] S. Anefalos Pereira et al. (The CLAS Collaboration), Phys. Lett. B 688, 289 (2010).

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γn à K*0Λ: Σ*- Overlap Cuts

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×

Studied potential interference:

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Varied Σ*- overlap cut width

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Nominal Σ*- Cuts: ±1Γ (70.5%)

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±0.5Γ (50.0%) & ±1.5Γ (79.5%)

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Differences (< 18%) < K*0 Fit ’s

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Potential interference < ’s

δσ δσ

Paul Mattione, Carnegie Mellon University Hadron 2013 November 5, 2013

γn à K+Σ*-: K*0 Overlap Cuts

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×

Studied potential interference:

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Varied K*0 overlap cut width

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Nominal K*0 Cuts: ±1Γ (70.5%)

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No cuts & ±2Γ (84.4%)

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Differences (< 4%) < Σ*- Fit ’s

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Potential interference < ’s

δσ δσ