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High momentum protons from 12 C fragmentation at intermediate energy

High momentum protons from 12 C fragmentation at intermediate energy. B.M.Abramov, P.N.Alekseev,Yu.A.Borodin,S.A.Bulychjov, I.A.Dukhovskoy, A.B.Kaidalov, A.I.Khanov, A.P.Krutenkova, V.V.Kulikov, M.A.Martemianov, M.A.Matsyuk, E.N.Turdakina,

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High momentum protons from 12 C fragmentation at intermediate energy

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  1. High momentum protons from 12C fragmentation at intermediate energy B.M.Abramov, P.N.Alekseev,Yu.A.Borodin,S.A.Bulychjov, I.A.Dukhovskoy, A.B.Kaidalov, A.I.Khanov, A.P.Krutenkova, V.V.Kulikov, M.A.Martemianov, M.A.Matsyuk, E.N.Turdakina, Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia • Motivation for nuclear fragmentation study • ITEP Heavy Ion Facility - TeraWatt Accumulator • Experiment FRAGM: 12C + A  F + X , T0 = 0.2- 3.2 GeV/n Momentum and kinetic energy spectra of fragments • x–distributions for 12C + Be  p + X and QGS model • Comparison with other experimental data • Conclusion Presented byA.P. Krutenkova NPD RAS Conference, Moscow, ITEP, 21-25.11.2011 A.P. Krutenkova, NPD RAS Session

  2. Motivation for nuclear fragmentation study • Measurement of nuclear composition of secondary beams at ITEP heavy ion accelerator. • 2. Precise measurement of high energy fragment spectra for • a) search for cumulative effect in fragment production • in heavy ion collisions, • b) test of theoretical models in the unstudied region of high momentum. • 3. Now systematic data are needed as input to transport codes for radiotherapy with heavy ions, for shielding calculation for long-duration space missions and for RIB design A.P. Krutenkova, NPD RAS Session

  3. ITEP Heavy Ion Facility: TeraWatt Accumulator U-10 Ring 10 GeV PS. 8×1011ppp 4GeV IS. 4×108 12C/cycle Material irradiation zone 25 MeV proton LINAC (I-2) Building for biological research and proton therapy Experiment FRAGM Area of fast extracted beam Areas of secondary beams from U10 Ring Target hall Areas of slow extracted beamsfrom U10 Ring Area of fast extracted beam from UK and U10 Rings UK Ring 400 MeV IS 2×109 ions/cycle Stand for radiation treatment of materials with high intensity beams Laser ion source 10 m Area of fast extracted beamfrom UK Ring A.P. Krutenkova, NPD RAS Session

  4. Experiment FRAGM 10m 16m 16m С-12 θ С А В Monitor - thin foil internal target Scintillation counters А 3(TOF+dE/dx) + H(20x10) B 2(TOF+dE/dx) Trigger = 1A ×1B C 14(TOF) 0.6 ×2.0 m×m - bending magnet - quadrupole 12C + Be  p (d, t, 3He, 4He, 6He, 8He,… ) + X, θ= 3.5O T0 = 0.2, 0.3, 0.6, 0.95, 2.0 and 3.2 GeV/n A.P. Krutenkova, NPD RAS Session

  5. Relative yields of H and He isotopes at 3.5o from 12C fragmentation on Be target at 300 MeV t Relative yield Rigidity =plab /Z, GeV/c (Z is fragment charge) Proton spectrum has non-Gaussian high momentum tail A.P. Krutenkova, NPD RAS Session

  6. Evaporation region tests Proton momentum spectrum in 12C rest frame(T0=300 MeV; fit with Gaussian from -0.2 to 0.1 GeV/c) Invariant cross section (a.u.) vs proton longitudinal momentum (GeV/c) In the rest frame of the nucleus, momentum distribution of a fragment has Gaussian shape. Parabolic law for r.m.s. of momentum distributions: σ2F= σ20AF(A – AF)/(A-1), (A, AF are masses of nucleus, fragment; σ is standard deviation) A.S. Goldhaber (1974) Limiting fragmentation hypothesis: fragmentation properties are independent of projectile energy and target mass. Preequilibrium region (“cumulative”) Kinematical limit for C+pp+X Evaporation region σ=0.073±0.002 GeV/c Gaussian PII, GeV/c Range of cross-section values covers eight orders of magnitude A.P. Krutenkova, NPD RAS Session

  7. Deuteron and triton momentum spectra (T0=300 MeV; fit with Gaussian ) χ2/ndf = 45.1/31 σ= .121±.005 GeV/c Ts = 4.3±0.5 MeV σ= .162±.003 GeV/c Forw. Backward Deuteron spectrum has sizeable high momentum non-Gaussian tail Triton spectrum is well described by Gaussian A.P. Krutenkova, NPD RAS Session

  8. Other Measurements Statistical Multifragmentation Model ALADIN GSI data Au+Au -> p+X at 1 GeV/n Hongfei Xi et al.(1997) A.P. Krutenkova, NPD RAS Session

  9. Slope parameters from kinetic energy spectra (Ed3σ/d3p ~ Asexp(-T/Ts) + Acexp(-T/Tc); T0=300 MeV) Invariant cross section (a.u.) vs rest frame kinetic energy T × sign (pII) (GeV) Ts = 4.3±0.5 MeV Tc= 18.9±0.6 MeV Protons Forw. Backward Kinetic energy spectrum can be described by two exponents A.P. Krutenkova, NPD RAS Session

  10. Tc and Ts energy dependences for 12C(scaling value for pA is ~50 MeV) T TC&TS, this experiment, C+Bep+X TC, M.Anikina et al, C+Cp+X, JINR (1986) TC&TS,T.Odeh et al, Au+Aup+X, GSI (2000) Tc Ts Slope of preequilibrium (“cumulative”) part increases with T0 from 16 to 44 MeV Theoretical approaches connect “cumulative” effect with contribution of multiquark states in nuclei A.P. Krutenkova, NPD RAS Session

  11. Production of cumulative particles • and Quark-Gluon String Model (QGSM) A.V. Efremov, A.B. Kaidalov, G.I. Lykasov, N.V. Slavin, Phys. Atom. Nucl. 57 (1994) 932 Abstract The production of cumulative particles in pA interaction was successfully considered in the framework of the QGSM. Assuming the existence of some coherent clusters in the nucleus and the asymptotic Regge behavior for their structure functions the distribution of quarks in the nucleus was derived and inclusive spectra of cumulative hadrons were analyzed. A.P. Krutenkova, NPD RAS Session

  12. Cumulative protons in QGSM Production of cumulative protons in fragmentation is considered as fragmentation into protons of clusters consisting of 3k valence quarks (k=1: (3q) - nucleon, k=2: (6q) – two-nucleon cluster, k=3: (9q) – three-nucleon cluster); wk is the probability to find k-nucleon cluster in 12C Ed3σ/d3p(x,pt2) =C’(w1g(x,pt2)+w2b2(x,pt2)+w3b3(x,pt2)) g(x,pt2)=G exp(-0.5 (1-x-D)2 /sx2 ) exp(-0.5 pt2/sp2 ) b2(x,pt2)=B2 (x/2)3 (1-x/2)3exp(-a1 pt2), b2(x,pt2)=0 at x>2 b3(x,pt2)=B3 (x/3)3 (1-x/3)6exp(-a2 pt2), b3(x,pt2)=0 at x>3 where g, b2 , b3 are known fragmentation functions. G, B2 and B3 are known normalization constants. Transverse parameters a1 anda2are from PRC 28 (1983) 1224 Fitted variables are: C’, W2=w2/w1,W3 = w3/w1,D ,sx A.P. Krutenkova, NPD RAS Session

  13. QGSM model fit of x=plab /p0 spectrum Invariant cross section, arbitrary unit 3q 6q 9q A.P. Krutenkova, NPD RAS Session

  14. x=plab /p0 spectra at different energies 3q 3(3q) 9q 3q 6q A.P. Krutenkova, NPD RAS Session

  15. Probabilities of quark clusters existence We used fitting procedure to get w2 and w3 K.S. Egiyan et al (2006) • Quantitative results on few nucleon clusters in nuclei could be obtained • from fragmentation data. • Wider range on x and wider projectile energy range are desirable A.P. Krutenkova, NPD RAS Session

  16. Conclusion • Light fragment momentum and kinetic energy spectra from reaction 9Be (12C, F)X were measured at T0 = 0.3-3.2 GeV/nucleon in evaporation and preequilibrium (“cumulative”) regions • Momentum spectra in evaporation region are well described • by Gaussians in accordance with SM. • Proton kinetic energy spectrum in “cumulative” region has exponential shape with slope parameter Tc which increases with projectile energy from 16 to 44 MeV. It shows that scaling behaviour is not reached at studied energy range. • Probabilities of existence of quark clusters in C-12 were estimated in QGSM. w2 ~10% and w3 <1% are in coincidence with those of two- and three-nucleon SRC measured at J-LAB A.P. Krutenkova, NPD RAS Session

  17. Backup slides A.P. Krutenkova, NPD RAS Session

  18. Parameters of x spectra Run 11_04_03 A.P. Krutenkova, NPD RAS Session

  19. Conclusion • Light fragment momentum and kinetic energy spectra from reaction 9Be (12C, F)X were measured at T0 = 0.2-3.2 GeV/nucleon. • Proton momentum spectra cover evaporation and preequilibrium (“cumulative”) regions; eight orders of magnitude in cross section • Momentum spectra in evaporation region are well described • by Gaussians • “Cumulative” region has exponential shape with slope parameter Tc increasing with initial energy from 16 to 44 MeV • Estimated probabilities of existence of quark clusters w2 ~10% and w3 <1% are in agreement with those of two- and three-nucleon correlations in 12C nuclei measured at J-LAB A.P. Krutenkova, NPD RAS Session

  20. ITEP-TWAC Operation Parameters A.P. Krutenkova, NPD RAS Session

  21. Relative yield of H and He isotopes at 3.50 from 12C fragmentation on Be target at 600 MeV Beam channel: rigidity P/Z=1.8 GeV/c/Z A.P. Krutenkova, NPD RAS Session

  22. Relative yield of H and He isotopes at 3.50 from 12C fragmentation on Be target Relative yield Rigidity =Plab /Z, GeV/c A.P. Krutenkova, NPD RAS Session

  23. Relative yield of H/He isotopes at 3.50 from 12C fragmentation on Be target at 600 MeV A.P. Krutenkova, NPD RAS Session

  24. He-3 and He-4 momentum distributions Ed3σ/d3p, relative units He-3 He-4 σ= .149±.003 GeV/c σ= .148±.003 GeV/c A.P. Krutenkova, NPD RAS Session

  25. He-6 and He-8 momentum distributions Ed3σ/d3p, relative units He-6 He-8 σ= .187±.007 GeV/c σ= .174±.009 GeV/c A.P. Krutenkova, NPD RAS Session

  26. Comparison with ALLADIN data Au+Au at 1000MeV/n for protons. T.Odeh et al. PRL84,4557(2000) Our data for C+Be at 300MeV/n - A.P. Krutenkova, NPD RAS Session

  27. x=plab /p0 spectrum at 300 MeV 3q 6q 9q A.P. Krutenkova, NPD RAS Session

  28. x=plab /p0 spectra at different energies 3q 3(3q) 9q 3q 6q A.P. Krutenkova, NPD RAS Session

  29. σF comparison with data and theoretical prediction Data: D.E.Greiner et al. PRL35,152(1975) Theoretical prediction: A.S.Goldhaber, PL53B,306(1974) (σF)2= (σ0)2F(Aproj. – F)/(Aproj,-1), where σ0 = 90 MeV/c 0.3 GeV/n 1.0 GeV/n this exp. Greiner et al. σ0 p 75.1±3.1 63±4 75.1±3.1 d 121.8±4.5 112±11 90.3±3.3 t 162.0±2.5 162±14 103.4±1.5 He-3 148.9±2.9 132±14 95.0±1.7 He-4 148.2±3.2 125±3 86.8±1.9 He-6 186.6±7.3 142±20 103.1±4.2 He-8 174.3±8.8 ------- 102.1±5.3 A.P. Krutenkova, NPD RAS Session

  30. Test of Goldhaber parabolic law This experiment – 0.3 GeV/n Greiner et al.- 1GeV/n σ0 = 94±1 MeV/c χ2 /ndf =96/6 σ0 = 74±2 MeV/c χ2/ndf =20/5 σ0 = 90 MeV/c used by SM A.P. Krutenkova, NPD RAS Session

  31. Interpretation of “cumulative” events • At high energies “cumulative” (x=plab /p0>1) production in pA was considered by Efremov, Kaidalov et al (1994) suggesting existence of multiquark clusters in nucleus and high energy behaviour of their structure functions in Quark-Gluon String Model (QGSM) • Kaidalov proposed to use FRAGM data to estimate the values of probabilities wk to find k-nucleon clusters in 12C (k=1,2,3) • Invariant cross-section was expressed as a sum of three terms: • Ed3σ/d3p(x,pt2)=C’(w1g(x,pt2)+w2b2(x,pt2)+w3b3(x,pt2)) • where g, b2 , b3 are known fragmentation functions (fragmentation through nucleon component (3q), two- (6q) and three- (9q) • nucleon clusters, respectively; details at backup slide). w1+w2+w3=1 A.P. Krutenkova, NPD RAS Session

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