PowerPoint Presentation - NSTAR 2009

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					   Workshop on the Physics of Excited Nucleon – NSTAR 2009, Beijing


Latest results from GRAAL collaboration
                                        presented by

                                   Valentina Vegna
                            on behalf of the GRAAL Collaboration

        Università degli Studi di Roma “Tor Vergata” and INFN Sezione di Roma Tor Vergata




               the GRAAL experimental set-up;
                and 0 photoproduction on quasi-free neutron;
               K+ and K+0 photoproduction on free proton;
               in memoriam of Eid Hourany.

Beijing, 19-22 April 2009                   NSTAR 2009                              Valentina Vegna
                            Meson Photoproduction at GRAAL

              GRAAL/ESRF
                                                            Beam Asymmetry Measurements
                                                               for accessible reactions:
                                                           • polarized photon beam;
                                                           • large acceptance apparatus;
                                                           • tagged photon beam.
 s (mb)




                                            E (GeV)
                                    ’ threshold
                                             


                                    K threshold
                             threshold

Beijing, 19-22 April 2009                          NSTAR 2009                         Valentina Vegna
                  GRAAL Polarized and Tagged Photon Beam
                                                                           green line
                                                                                  UV line
                                 E
                                      
     e-                                                    L
               Ee,me                     
                                                   EL
                                          E’e, me e-

  Ee= 6 GeV
  EL= 2.41 eV (green line, l = 514 nm)              Emax= 1.1 GeV
  EL= 3.53 eV (U.V. line, l = 351 nm)               Emax= 1.5 GeV


               Tagger                     Energy Spectrum            Energy Resolution

                                                                     16 MeV FWHM




Beijing, 19-22 April 2009                     NSTAR 2009                        Valentina Vegna
                                   GRAAL Detector


           NOT IN SCALE




                 Photon detection (energy resolution 3% FWHM at 1 GeV);
                 Charged particle identification (protons - pions);
                 Energy measurement for protons;
                 Neutron detection (and energy measurement in forward direction).

Beijing, 19-22 April 2009                   NSTAR 2009                          Valentina Vegna
                                Measurement at GRAAL
 Experimental Distribution at fixed E and mCM:            NH,V  kH,V ε 1  PΣ cos(2 ) 


                                NV /KV      1
                                             (1  Pcos(2  ))
                            NV /KV  NH /KH 2

                                                                         
         n p     n p           n p    0  n p               p  k  




                                              deg 
                                               0




Beijing, 19-22 April 2009                    NSTAR 2009                               Valentina Vegna
         Photoproduction on Quasi-Free Nucleon in Deuteron
                                                                         A.Fantini et al., Phys.Rev.C 78, 015203 (2008)
               pn   pn                   n p   n p 
                                           1                                                         3
   Preselection:                                                  Selection cuts:
   2 neutral cluster detected in BGO
   (invariant mass  (0.35-0.7) GeV/c2);
                                                         •      meas
                                                                  N        N  vs N   180
                                                                             calc     meas meas


   1 neutron or 1 proton (in the central or
   in the forward detectors);
   no other particles.

                                           2
    Kinematic Analysis:
    •    Two-body nature of each reaction
         step:
                                                         •   E    calc
                                                                          E  vs M  M N 
                                                                            meas     miss




         E                          Ncalc

                                   
        Emeas meas       meas   Ecalc
                N
                 meas
                             N  M miss
                              meas
                                   


Beijing, 19-22 April 2009                         NSTAR 2009                                             Valentina Vegna
                        in  Photoproduction on qfp and fp
                                                           A.Fantini et al., Phys.Rev.C 78, 015203 (2008)

                                                                          qfp
                                                                          fp

                                                                           MAID2001 - fp
                                                                           reggeized model - qfp
                                                                           MAID2001 - qfp




 • at low energies:     sin 2   dependence
                                CM
                                                 D13 1520 
 • with increasing energy: forward-backward asymmetry          F15 1670 
Beijing, 19-22 April 2009                    NSTAR 2009                                Valentina Vegna
                             in  Photoproduction on qfn
                                                         A.Fantini et al., Phys.Rev.C 78, 015203 (2008)


                                                                                     qfn
                                                                                    reggeized model

                                                                                    MAID2001




                                                                                  D15 1675 




                                                          E  0.9GeV : symmetric behaviour
                                            0.9GeV  E  1.25GeV : peak in forward direction
                                                         1.25GeV  E : symmetric behaviour
Beijing, 19-22 April 2009               NSTAR 2009                                   Valentina Vegna
                       in  Photoproduction on qfp and qfn
                                                   A.Fantini et al., Phys.Rev.C 78, 015203 (2008)


                                                                                         qfn
                                                                                         qfp




                                                              up to 1.05 GeV:
                                                                  qfn quite close to qfn;
                                                              above 1.05 GeV:
                                                              •   P11(1670);
                                                              •   S11(1650)-P11(1710).

Beijing, 19-22 April 2009             NSTAR 2009                               Valentina Vegna
        0 Photoproduction on Quasi-Free Nucleon in Deuteron
                                                                                     R. Di Salvo, to be submitted
               pn    0 pn                 n p    0 n p 
                                           1                                                            3
   Pre-selection:                                                    Selection cuts:
   2 neutral cluster detected in BGO
   (invariant mass  (0.09-0.20) GeV/c2);                   •      meas
                                                                     N       N  vs N   0 180
                                                                               calc     meas meas


   1 neutron or 1 proton (in the central or
   in the forward detectors);
   no other particles (quasi-free kine).

                                           2
    Kinematical Analysis:
    •    Two-body nature of each reaction
         step:
                                                            •         E
                                                                           calc
                                                                            0     E 0  vs M miss to π 0
                                                                                   meas




         E                          Ncalc

                                   
        Emeas meas
           0      0         meas   Ecalc
                               0          0


                N
                 meas
                             N  M miss
                              meas
                                         0




Beijing, 19-22 April 2009                          NSTAR 2009                                               Valentina Vegna
                       in 0 Photoproduction on qfp and fp
                                                     R. Di Salvo, to be submitted




                                                                             fp
                                                                             qfp


Beijing, 19-22 April 2009             NSTAR 2009                        Valentina Vegna
                             in 0 Photoproduction on qfn
                                                        R. Di Salvo, to be submitted


                                                                                 qfn

                                                                            MAID2007

                                                                            MAID2007 new




Beijing, 19-22 April 2009               NSTAR 2009                         Valentina Vegna
                          in 0 Photoproduction on qfn
                        Multipole extraction in MAID2007
         Immaginary part         Real part



                                                     P 1700 
                                                      11
                                                      tot  70MeV
                                                        0.1




                                                     P 1720 
                                                      13




                                                        MAID2007 qfn
                                                        mod MAID2007 qfn


Beijing, 19-22 April 2009               NSTAR 2009                   Valentina Vegna
                      in 0 Photoproduction on qfp and qfn
                                                         R. Di Salvo, to be submitted


                                                  qfn
                                                  qfp
                                                  MAID2007 “new” for neutron
                                                  MAID2007 “new” for proton




Beijing, 19-22 April 2009            NSTAR 2009                             Valentina Vegna
          K+ and K+0 Photoproduction on Free Proton
                                            A.Lleres et al., EPJ A 31, 79-93 (2007)
                             
      p  K   K p
                       
                              p  K   0  K    K  p 
                                     1                                             3
          Preselection:                           Selection cuts:
          3 tracks + at most 1 neutral            • Energy balance;
          cluster detected in BGO                 • Charged particles mass;
          (no neutral particle: K+; 1            • Missing mass    mpK    ;
          neutral particle: K+0)
                                                  • Energy of the  from  decay.

                                     2                                             4
          Kinematic Analysis:                      Check:  decay length

          •    Three-body kinematics;
          •    Two-body nature        of
               each reaction step;
                            
                           p  K   0
          p  K  
            p            0  
                              p
Beijing, 19-22 April 2009                  NSTAR 2009                                  Valentina Vegna
                             in K+ and K+0 Photoproduction
                                                          A.Lleres et al., EPJ A 31, 79-93 (2007)




                                     GRAAL                          GRAAL
                                     Ghent Isobar
                                                                   Published Bonn coupled channel
                                     Saclay
                                     Bonn coupled                  New Bonn coupled channel
                                          channel



Beijing, 19-22 April 2009                    NSTAR 2009                          Valentina Vegna
                            P in K+ Photoproduction
                                                                 A.Lleres et al., EPJ A 31, 79-93 (2007)


                                                       W cos p  
                                                                       1
                                                                       2
                                                                              
                                                                         1   P cos p   
                                                           2 N cos p 0   N cos p 0 
                                                      P 
                                                            N cos p 0   N cos p 0 
                                                             0.642  0.013
                                                 From  and P measurements:
                                                  • Saclay Model:
                                                         S11 1700  P 1800  D13 1850 
                                                                      13

                                                  • Ghent Isobar Model:
                                                                        D13 1900 

                                  GRAAL
                                                  • Reggeized Model:
                                  CLAS
                                                               P 1900  D13 1900 
                                                                13
                                  Ghent Isobar
                                  Saclay          • Bonn Coupled Channel Model:
                                  Bonn coupled
                                       channel                           D13 1875 
Beijing, 19-22 April 2009                NSTAR 2009                                     Valentina Vegna
      Formalism for Recoil Observables in K+ Photoproduction
      ds 1  ds 
f              [1  P  cos 2  s x ' P Ox sin 2  s y ' P  P T cos 2   s z ' P Oz sin 2 ]
      d  2  d  0

                 P  P T cos 2                     S1                                          P Ox , z sin 2                   S4 S3
          P 
            y'
                                               S2          S2                   P  x ', z '
                                                                                              
           
                  1  P  cos 2
                                                                                  
                                                                                                  1  P  cos 2                    S3 S4
                                                      S1


           <Py’>           S1            S2                                      <Px’,z’>                 S3               S4
                         P  2 P T   P  2 P T                                                         2 P Ox , z       2 P Ox , z
           lab=0°                                                                    lab=0°                           
                                                                                                                                 
                           2P        2 P                                                                
                         P  2 P T   P  2 P T                                                         2 P Ox , z       2 P Ox , z
          lab=90°                                                                lab=90°             
                                                                                                               
                                                                                                                         
                                                                                                                                 
                           2 P       2P 



                                                                  2
                                                                        
                                                     W cos p   1   P cos p
                                                                  1
                                                                                              
                        1      P  2 P T                                                        1                            
                                                                             W cos p ', z '   1    x , z cos p ', z ' 
                                                                                                           2P O
          W cos py '  1               cos py ' 
                                                                                        x                                x

                        2
                                 2 P             
                                                                                                   2
                                                                                                                                
                                                                                                                                  


                                       P  2 P T                                                                                        
    1y'
                    
 N  N 0y'   cos py '        
                                 1  
                                         2 P 
                                                         y' 
                                                    cos p
                                                            
                                                                       N  ', z ' 
                                                                         x
                                                                                        N 0   cos p ', z ' 1    x, z cos p ', z ' 
                                                                                      1 x ', z '       x
                                                                                                                 
                                                                                                                       2P O         x
                                                                                                                                             
    2                                                                               2                                                    

Beijing, 19-22 April 2009                                       NSTAR 2009                                                            Valentina Vegna
     Double Polarization Observables in K+ Photoproduction
                                                                      A.Lleres et al., EPJ A 39, 149-161 (2009)
          2N ' x
                            2 P Ox      x                2N ' z
                                                                              2 P Oz      z 
                     1           cos p '                         1           cos p ' 
         N '  N ' 
          x       x
                                            
                                                          N '  N ' 
                                                            z       z
                                                                                              
                                                                                                




                                        GRAAL                                                     GRAAL
                                        GI RPR                                                   GI RPR
                                        Bonn Gatchina                                            Bonn Gatchina




Beijing, 19-22 April 2009                         NSTAR 2009                                  Valentina Vegna
                            T in K+ Photoproduction
                                                                       A.Lleres et al., EPJ A 39, 149-161 (2009)


                                                                                P  2 P T           
                                                                           1              cos py ' 
                                                2 N y '          2 P          2 P            
                                                                1 
                                                                         
                                             N y '  N y '                1  P cos py '      
                                                                                                       
                                                                                                      
                                                                                                      


                                                 From Ox, Oz and T extractions:

                                                        • Ghent Isobar RPR Model:
                                                           S11 1650  P 1710  P 1720 
                                                                        11        13


                                                                P 1900  D13 1900 
                                                                 13


                                  GRAAL                 • Bonn Gatchina Model:
                                 GI RPR
                                 Bonn Gatchina         S11 1535  S11 1650  P 1720  P 1840 
                                                                                13        11


                                                                      P 1900 
                                                                       13

Beijing, 19-22 April 2009                NSTAR 2009                                            Valentina Vegna
                                Comparison with CLAS
                                                        A.Lleres et al., EPJ A 39, 149-161 (2009)
    1 T    O  O  P  C  C
           2     2      2
                        x
                            2
                            z
                                 2   2
                                     x
                                         2
                                         z
                                                      C z Ox  C x Oz  T  P




Beijing, 19-22 April 2009                NSTAR 2009                             Valentina Vegna
                                             Conclusions
•  photoproduction on nucleon:
       measurement of  in the energy range from 0.7 to 1.5 GeV;
       qfp is similar to fp: it suggests that qfn is similar to fn;
       the energy dependence of qfp and qfn is very similar up to 1.05 GeV;
       above 1.05 GeV, qfp is forward peaked while qfn looks more symmetric around CM = 90°;
       above 1.05 GeV and backward angles, qfn is substantially higher than qfp;


• 0 photoproduction on nucleon:
       measurement of  in the energy range from 0.5 to 1.5 GeV;
       qfpis similar to fp : it suggests that qfn is similar to fn;
       qfp and qfn are very similar for low values of 0* but differ a lot with increasing of 0*;


• K+ photoproduction:
       systematic measurements of , P, Ox, Oz and T in the energy range from 0.9 to 1.5 GeV;
       comparisons with 4 different models confirm the necessity to introduce new or poorly
      known resonances in the 1900 MeV mass region: P13and/or D13;
       we need only one additional double-polarization observable to extract helicity amplitudes.

Beijing, 19-22 April 2009                          NSTAR 2009                               Valentina Vegna
                            In memory of Dr. Eid Hourany
                                             Dr Eid HOURANY died in October
                                             2008 at the age of 67.

                                             He had been involved as the leader of
                                             the Orsay team in the GRAAL
                                             venture since the beginning and
                                             constructed the scintillating wall of
                                             the GRAAL detection system.

                                             He    has     been     a     talented
                                             experimentalist able to analyse
                                             complex data. In the last few years,
                                             he has analyzed almost alone,
                                             « exotic » final states as: Nπ0π0,
                                             Nπ0η, Nω and extracted from the
                                             GRAAL      data   very     innovative
                                             information.
                                             The quality of the GRAAL physics
                                             production is largely indebted to his
                                             constantly demanding attitude.

Beijing, 19-22 April 2009              NSTAR 2009                       Valentina Vegna
                             Double 0 photoproduction
        ...on the proton                          ...on the neutron



        P 1440
         11

       D13 1520




                            P 1710 
                             11

                            D13 1700




             P.R.L. 90 (2003)                         Phys.Lett.B 651 (2007)


Beijing, 19-22 April 2009                NSTAR 2009                            Valentina Vegna
                             photoproduction on the proton




                                                  D131520 P 1720 F 1680
                                                             13       15




                                     P.R.L. 96 (2006)
Beijing, 19-22 April 2009                 NSTAR 2009                       Valentina Vegna
                     Simultaneous  and 0 photoproduction

                                                        3-body phase space
                                                        
                                                        γ p  π 0S11, S11  ηp

                                                         
                                                         γ p  ηΔ, Δ  π 0p

                                                        Döring, Oset,
                                                        Strottman (2006)




                            P.R.L. 100 (2008)
Beijing, 19-22 April 2009                  NSTAR 2009             Valentina Vegna
                  Thanks a lot
               for your attention


Beijing, 19-22 April 2009   NSTAR 2009   Valentina Vegna
                 0 Photoproduction: Re-calculation of  C.M.             0

                                                               R. Di Salvo, to be submitted


      
     P  PF                        Deviation of the Lorentz Boost Axis

             extr 
   PF  P 0  PN  P 
                                            Re-calculation of 0
                                                                    C.M.
         




       EN  E  M N  E
        extr



       P extr
         N           E   extr 2
                            N         MN
                                        2




Beijing, 19-22 April 2009                      NSTAR 2009                         Valentina Vegna
                         Photoproduction: Selected Events
                                                   Fantini et al., Phys.Rev.C 78, 015203 (2008)
     central region
     forward region    proton       neutron




                                                         Total exstimated background

                                                                      Proton     Neutron

                                                           Centre      2.4%        3.9%

                                                          Forward      0.9%        1.4%




Beijing, 19-22 April 2009             NSTAR 2009                               Valentina Vegna
                                 Photoproduction: Check
                                                              Fantini et al., Phys.Rev.C 78, 015203 (2008)



 Check on the validity of:




                                        3-parameters fit:




                            Similiar results for  beam asymmetry;
                            Higer 2;
                            The quality of fits gets worse.




Beijing, 19-22 April 2009                      NSTAR 2009                                Valentina Vegna
                            P0 in K+0 Photoproduction
                    
                    p  K   K   K p 
                           0           




                                                 
                                        
                                P   P0  u u

        u , unity vector along the direction of  emission in the 0 rest frame




                                      1
                                P   P0
                                      3

Beijing, 19-22 April 2009                  NSTAR 2009                      Valentina Vegna
  K+ Photoproduction : Efficiency Dependence for N+ and N-
                                                   Lleres et al., EPJ A 31, 79-93 (2007)


                                           cos p '     cos p ' 
                                                   x                 x


                                          via Monte Carlo simulation




                                      2N ' 
                                           x
                                                                  2N ' 
                                                                       x

                                      N  N x' 
                               Cor   x '                       x'
                                                                  N  N x' 
                                                                            
                                             gen                     sel




                                  Detection efficiencies and correction factors
                                  depend on the input values of Ox , Oz and T:
                                  iterative method (3 iterations).




Beijing, 19-22 April 2009   NSTAR 2009                                   Valentina Vegna
                                              Internal Check
                                                               A.Lleres et al., EPJ A 39, 149-161 (2009)
               P O O 1
                 2     2
                       x
                            2
                            z

                2  Ox  Oz2  1
                      2
                                                                 T  P  1 
               1  T 2  P 2  Ox  Oz2  1
                                2




Beijing, 19-22 April 2009                         NSTAR 2009                           Valentina Vegna
       Photoproduction: theoretical models for comparisons
                                           Fantini et al., Phys.Rev.C 78, 015203 (2008)




Beijing, 19-22 April 2009     NSTAR 2009                              Valentina Vegna
              Models in K photoproduction off free protons
SACLAY
                                        G.I.




                                        BCC




GRPR




 Beijing, 19-22 April 2009        NSTAR 2009              Valentina Vegna

				
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