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Charmed Baryon Production (Charmed baryon Spectroscopy via p( -,D* - )Y c ) 11 Sep., 2013 H. Noumi RCNP, Osaka University 1
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2 What are good building blocks of Hadrons? Constituent Quark q q q q q Diquark? [qq] q (Colored cluster) hadron (colorless cluster) q q q q q
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How to form baryons? 3 q q q Most fundamental question Interaction btwn quarks Diquark correlations 3 [qq]-pairs in a Light Baryon How to close up diquark correlations
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Charmed Baryon 4 Q qq Weak CMI with a heavy Quark [qq] is well Isolated and developed Level structure of Y c * Decay Width/Decay Branching Ratios, etc. V CMI ~ [ s /(m i m j )]*( i j )( i j )
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5 Hydrogen Target 20 GeV/c Beam Dispersive Focal Plane High-resolution, High-momentum Beam Line High-resolution, High-momentum Beam Line D* Spectrometer Missing Mass Spectrum Missing Mass Spectroscopy Measure D* - Charmed Baryon Spectroscopy (P50)
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Charmed baryon spectrometer Modified design FM cyclotron magnet J-PARC E16 ⇒ 2.3 Tm, 1 m gap High rate detectors Fiber, SSD Large detectors Internal detectors DC, RPC PID: RICH Hybrid radiator LH 2 -target Ring Image Cherenkov Counter Internal DC FM magnet ss SSD Fiber tracker Beam GC Internal TOF DC TOF wall 2m Decay Beam Large acceptance multi-particle spectrometer system Multi propose spectrometer
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* D* tagging: > 10 6 reduction ⇒ Other event selection ○ Forward scattering angle cut ⇒ Reduction (2.2-3.4 GeV/c 2 ) = 15 Signal acceptance = 0.54 1900 → 1000 counts Background reduction 3 K cm KK ss D0sD0s DD Reduction S/N D0 15×2.0×10 6 reduction background W/ signals
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Background spectrum Clear peak structure @ 1 nb/peak case * Main background structure is dominant. ⇒ Achievable sensitivity: 0.1-0.2 nb (3 level, < 100 MeV) Sum Main BG (s-production + Miss-PID) Associated charm production BG W/o signal W/ signal: 1900 counts/peak W/ signal: 1000 counts/peak W/o signal Only D* taggingW/ event selection
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Decay measurement Method: Mainly Forward scattering due Lorentz boost ( < 40°) Horizontal direction: Internal tracker and Surrounding TOF wall Vertical direction: Internal tracker and Pole PAD TOF detector Mass resolution: ~ 10 MeV(rms) Only internal detector tracking at the target downstream PID requirement: TOF time difference ( & K) ⇒ T > 500 ps Decay particle has slow momentum: < 1.0 GeV/c Beam Target Magnet pole Beam Target Internal tracker Pole PAD TOF wall Surrounding TOF wall Magnet pole
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Basic performances Acceptance 50 60% ○exp(bt) (t-channel, b = 2 GeV 2 ) Yield @ 1 nb case: ~1900 counts ○4 g/cm 2 LH 2 target, 8.64×10 13 (100 days) ○ all = 0.55 Acceptance for decay particles: ~85% ○ c (2940) + → c (2455) 0 + ○ c (2940) + → p D 0 * Compare coverage cos > 0.5 Resolution p/p = 0.2% @ 5 GeV/c Invariant mass resolution ○D 0 : 5.5 MeV ○Q-Value: 0.7 MeV Missing mass resolution ○ c + : 16.0 MeV ○ c (2880) + : 9.0 MeV Decay measurement ○ M ~10 MeV exp(bt) Isotropic in CM Acceptance: D* detection Decay angle: c (2940) + → c (2455) 0 + Forward direction (Beam direction)
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Tagged missing mass spectra * Full event w/ background @ 1 nb Continuum background around the peak region Signal counts c mode: ~230 counts p D mode: ~320 counts c 0 c ++ c + p D 0 SUM Signal Main BG c0c0 c ++ c+c+ D0D0
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Tagged missing mass spectra * Full event w/ background @ 1 nb Selecting c + decay chain ⇒ Background level was drastically decreased. Signal counts c mode: ~230 counts ⇒ ~200 counts p D mode: ~320 counts c 0 c ++ c + p D 0 SUM Signal Main BG c0c0 c ++ c+c+ D0D0
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What We can Learn from P50… Production Cross Section Not only for feasibility but also… – Production Mechanism (Hosaka-san) Does the Regge model work? (large s & small |t|) – Coupling Constant/Form Factor -> LQCD? What does the state population tell us? – Spin/Isospin Structure – Wave Functions (Q-Diq picture or others) – So-called rho-mode (di-quark) excitation? – Application of pQCD (Kawamura-san) Applicable at large s &|t| (Hard process)? Prediction from pQCD Are there any feedback from the P50 measurement?
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What We can Learn from P50… Expected Spectrum – Excitation Energy and Width Baryon Structure Can we see a Quark-diquark picture? Decay Property – Decay branch/partial width Baryon Structure – (Y c * -> pD)/ (Y c * -> c ) ? – Angular Distribution Spin/Parity
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Charm production Cross Section No exp. data for the p( ,D* ) c is available but σ<7nb at p =13 GeV/c at BNL (1985)
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Charm production Cross Section Photoprod. of c D* bar X on p at E =20 GeV. – ( c D bar X ) =44±7 +11 -8 nb – (D - X)=29±5 +7 -5 nb – (D* - X)=12±2 +3 -2 nb ( c D* bar X ) ~ 18 nb This seems sizable. Abe et al., PRD33, 1(1986) D* C, X p
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Charm production Cross Section ( N→J/ψX) = ( 1±0.6 ) nb and (3.1±0.6)nb at 16 GeV/c and 22 GeV/c. – OZI-suppressed process! J/ψ X N LeBritton et al., PLB81, 401(1979)
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Comparison in strange sector OZI-suppressed process in Strange Sector – ( p→ n) = ( 1.66±0.32 ) nb at 4 GeV/c. – ( p→ p) = ( 9.5±2.0 ) nb at 3.75 GeV/c -> ( N→ N)/ ( N→ X)~1/10? OZI-non-suppressed process – ( p→ ) = ( 53±2 ) nb at 4.5 GeV/c -> ( p→ )/ ( N→ X)~2? -> ??? ( p→D c )/ ( N→J X)~2? Crennell et al., PRD6, 1220(1972) Avres et al., PRL32, 1463(1973) Gidal et al., PRD17, 1256(1978)
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Comparison in strange sector s/s 0 ( b) ∝s-∝s-
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Theoretical Estimations t-channel PS meson exchange Comment on the pQCD model Regge Model: revisit
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Revisit the Regge Theory shows the typical s-dependence of binary reaction cross sections at the large s region; – Regge trajectory: – scale parameter s 0 : s at the threshold energy of the reaction AB → CD (*In Kaidalov’s Model: s 0 2( D* (0)-1) =s CD 0)-1 *s CD J/ 0)-1 s AB =( Σ m i ) A *( Σ m j ’) B, m i :transversal masses of the consituent quark) Treatment of (- (t)) to avoid possible singularities – Actually introduce phenomenological form factor (- (t)) → (- (t 0 )): naïve Regge → (1- (t 0 )) : Kaidalov’s Regge [Z. Phys. C12, 63(1982)] → exp(R 2 t): Grishina’s Regge [EPJ A25, 141(2005)] discussed with A. Hosaka
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Regge Theory PS(K,D)-Regge (Top): s/c-prod: ~10 -5 (Naïve), ~3x10 -5 (Kaidalov) V(K*,D*)-Regge (Bottom): s/c-prod.: ~10 -4 (Naïve), ~3x10 -5 (Kaidalov) calculated by A. Hosaka (0) T 1/2 (GeV) K-0.1513.652.96 D-1.6113.654.16 K*-0.4143.652.58 D*-1.0203.653.91 s/s (arb.) s/s s 0 (GeV 2 ) Naïve K* K* c 4.02 18.46 Kaidalov K* K* c 1.66 4.75 Regge Trajectory Scale Parameter p =20 GeV/c
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Regge Theory Normalization with (p( -,K*) ) data [ PR163, 1377(1967), PRD6, 1220(1972) ] – Naïve Regge shows a steeper s-dependence – Grishina’s Regge with R 2 =2.13 GeV -2 reproduces data well. Charm production: ~10 -4 of strangeness production, → We expect (p( -,D*) c ) close to 10 nb at p =20 GeV/c. s/s ( b/sr) (- (t 0 )) exp(R 2 t) (- (t 0 )) exp(R 2 t) (- (t 0 )) exp(R 2 t) (p( -,K*) )/ (p( -,D*) c ) s/s p( -,K*) p =20 GeV/c p( -,D*) c Ratio of s- to c-prod.
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Comment on the Coupling Constant Comparison of g D*D* /g K*K* and g cND /g NK* – Estimated by means of the Light Cone QCD Sum Rule – Exp. Data Taking g D*D* /g K*K* g cND* /g NK* → We expect (p( -,D*) c ) a few nb. g K*K* g D*D* g D*D* /g K*K* 3.5*4.51.3 g K*K g D*D g D*D /g K*K 4.5*7.51.7 A. Khodjamirian et al. EJPA48, 31(2012) g NK* g cND* g cND* /g NK* -6.1 +2.1 -2.0 -5.8 +2.1 -2.5 0.95 +0.35 -0.28 g NK g cND g cND /g NK 7.3 +2.6 -2.8 10.7 +5.3 -4.3 1.47 +0.58 -0.44 g K*K g D*D g D*D /g K*K ~4.58.95 +- 0.15+-0.9 ~2+-0.2 M.E. Bracco et al. Prog. Part Nucl. Phys. 67, 1019(2012) *note:g[Bracco]/2=g[Khodjamirian] 24
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25 λ and ρ motions split known as isotope shift q q, SO c (1/2-,3/2-) Λ c ( 1/2-,1/2- 3/2-,3/2-, 5/2- ) Λ c (1/2-,3/2-) Σ c (1/2-,1/2- 3/2-,3/2-, 5/2- ) c (1/2+,3/2+) Λ c ( 1/2+ ) “Q” may isolate “qq” q q q Q q-q Q λ mode ρ mode G.S. 25 Hosaka-san
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Excitation Energy Dependence Production Rate in a quark-diquark model: – D* exchange at a forward angle – Radial integral of wave functions Taking Harmonic Oscillator Wave Functions I ~ (q eff /A) L exp(-q eff 2 /2A 2 ) I ~ (q eff /A) L exp(-q eff 2 /2A 2 ), where A: oscillator parameter (0.4~0.45 GeV) q eff ~ (q eff /A) L For larger q eff, the relative rate of a higher L state to the GS increases as ~ (q eff /A) L – Spectroscopic Factor: pick up good/bad diquark configuration in a proton A residual “ud” diquark acts as a spectator – Kinematic Factor w/ a propagator : – Spin Dependent Coefficient, C: Products of CG coefficients based on quark-diquark spin configuration Characterized by the spin operator in the vector meson exchange, u c “ud” D* f g YcYc p discussed by A. Hosaka =1/2 for c ’s =1/6 for c ’s
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Estimated Relative Yield p =20 GeV/c c 1/2+ 2286 c 1/2+ 2455 c 3/2+ 2520 c 1/2- 2595 c 3/2- 2625 c 1/2- 2750 c 3/2- 2820 c 1/2- 2750 c 3/2- 2820 c 5/2- 2820 c 5/2+ 2880 1/21/6 1/2 1/6 ½ C11/98/91/32/31/272/27 56/1352/53/5 K0.860.950.940.85 0.920.910.920.91 0.83 q eff 1.331.431.441.371.381.491.501.491.50 1.41 R (Rel.) 10.030.201.172.260.030.060.070.330.311.55 The estimation is valid for the D* exchange at a very forward angle. The yields for some of c ’s are suppressed due to and C. The C coefficient is characterized by spin dependent interaction at the D*NY c vertex. Those for c ’s are not suppressed very much at the excited states. |I| reduces (increases!) an order of (q eff /A) L at higher L states. 27 calculated by A. Hosaka
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Estimated Relative Yield (strange sector) p =4.5 GeV/c 1/2+ 1116 1/2+ 1192 3/2+ 1385 1/2- 1405 3/2- 1520 1/21/6 1/2 C11/98/91/32/3 K1.021.231.170.990.97 q eff 0.290.310.380.360.40 R (rel.)10.050.290.090.17 Exp( b/sr) 318+-12186+-2829+-632+-760+-13 The yield for 1/2+ is suppressed due to and C. The estimation is not very far from the experimental data but for ’s. This already suggests a necessary modification of the model. The measurement in charm sector provides valuable information on the reaction mechanism and structure of baryons. Exp.: p( ,K 0 )Y, D.J. Crennell et al., PRD6, 1220(1972) 28 calculated by A. Hosaka
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Production Rate 29
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30 c (1/2 + ) c (1/2 - ) (1/2 + ) (1/2 - ) q eff =1.33 GeV/c q eff =1.37 GeV/c q eff =0.29 GeV/c q eff =0.27 GeV/c L=0 r {fm} L=1 charm strange
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Summary… Experimental Design – 1000 count/nb/100d – Background reduction Signal Sensitivity: 0.1~0.2 nb for ~100 MeV state 1 Decay particle detection inprove S/N very much – Improve the acceptance Decay particle Acceptance Production Rate – A few nb for c production seems a plausible estimation Excitation Energy Dependence – The production rate is kept even at higher L spin/isospin structures – The production rate is kept even at higher L states, depending on spin/isospin structures of baryons. – How are the rho-mode states excited? How can we extract “diquark” in baryons Can we can learn characteristic baryon structures from – Excitation Energy Spectrum – Population (Production Rate) – Decay (Partial) Width/Branching Ratio – Angular Correlation – What is similarity to/difference from strange baryons 31
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Structure and Decay Partial Width 32 Excited (qq)Good [qq] (1520) -> NK (D wave!)>π , similarly (1820), (2100) Possible explanation of narrow widths of Charmed Baryons Illustrated by Hosaka
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33 Possible Subjects Charmed Baryon Spectroscopy N*, Y* resonances via ( ,ρ), ( ,K*) ’, , , J/ , D, D* productions off N/A “K - K - pp” strongly interacting hadronic system S=-1, -2, -3 baryon spectroscopy w/ K beam others We welcome you to join !
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