Download presentation

Presentation is loading. Please wait.

Published byNathan Audrey Modified over 2 years ago

1
0, , + exclusive electroproduction on the proton at CLAS on the proton at CLAS

4
,

5
Regge theory: Exchange of families of mesons in the t-channel

7
Regge theory: Exchange of families of mesons in the t-channel M(s,t) ~ s (t) where (t) (trajectory) is the relation between the spin and the (squared) mass of a family of particles M->s (t) tot ~1/s x Im(M(s,t=0))->s (0)-1 [optical theorem] tot d /dt s t d /dt~1/s 2 x |M(s,t)| 2 ->s (t)-2 ->[e (t)lns(s) ]

8
,

9
, Q 2 >>

10
,

11
Some signatures of the (asymptotic) « hard » processes: L / T ~Q 2 J ~9/1/2/8 L ~1/Q 6 T ~1/Q 8 ~|xG(x)| 2 Q 2 dependence: W (or x B ) dependence: (for gluon handbag) Ratio of yields: (for gluon handbag) Saturation with hard scale of P (0), b, … SCHC : checks with SDMEs

12
H1, ZEUS, Q 2 >> H1, ZEUS CLAS HERMES COMPASS + « older » data from: E665, NMC, Cornell,…

13
H1, ZEUS, Q 2 >> H1, ZEUS CLAS HERMES COMPASS + « older » data from: E665, NMC, Cornell,…

15
Ratios J ~ 9/1/2/8 1/sqrt(2){|uu>-|dd>} 1/sqrt(2){|uu>+|dd>} Ratio =9

16
For W>5 GeV, good indications that the “hard”/pQCD regime is reached/dominant for is reached/dominant for 2 =(Q 2 +M V 2 )/4 ~ 3-5 GeV 2. Data are relatively well described by GPD/handbag approaches Great, one can hope to learn about the gluon (transverse) spatial distribution in the nucleon, the gluon orbital momentum contribution to the nucleon spin, etc…

17
H1, ZEUS, Q 2 >> H1, ZEUS CLAS HERMES COMPASS

18
Exclusive 0, electroproduction on the proton @ CLAS6 on the proton @ CLAS6 S. Morrow et al., Eur.Phys.J.A39:5-31,2009 ( 0 @5.75GeV) J. Santoro et al., Phys.Rev.C78:025210,2008 ( @5.75GeV) L. Morand et al., Eur.Phys.J.A24:445-458,2005 ( @5.75GeV) C. Hadjidakis et al., Phys.Lett.B605:256-264,2005 ( 0 @4.2 GeV) K. Lukashin et al., Phys.Rev.C63:065205,2001 ( @4.2 GeV) } e1-b (1999) } e1-6 (2001-2002) A. Fradi, Orsay Univ. PhD thesis ( @5.75 GeV) } e1-dvcs (2005) F.-X. Girod

19
Exclusive 0 electroproduction

20
e1-6 experiment (E e =5.75 GeV) (October 2001 – January 2002)

21
ep ep + ( - ) Mm(epX) Mm(ep + X) e p ++ - )

22
1) Ross-Stodolsky B-W for 0 (770), f 0 (980) and f 2 (1270) with variable skewedness parameter, 2) ++ (1232) + - inv.mass spectrum and + - phase space. Background Subtraction

23
IM(p + )

24
IM(p - )

25
V. Mokeev 2 e-prod model Working up to W=1.6 GeV up to Q 2 ~1 GeV 2

27
J-M. Laget 2 e-prod model +f 0 + f 2

28
+f 0 + f 2 all (incl. 0 ) Good description of CLAS,SLAC data Laget model: Photoproduction

29
Laget model: Electroproduction CLAS data Laget model

30
At the time of the analysis (~2008), radiative corrections were treated as averaged over M + -, i.e. only as a function of (x B, Q 2 ) Relatively small effect on 0 cross sections as the “distortion” of the M + - spectrum was “absorbed” in the effective + - continuum background subtraction (also ~25% syst. uncertainty was included) M + - (GeV) However, current more refined re-analysis of these data (B. Garillon, aimed at f 0 and f 2 analysis, see talk on Saturday) show that there is a M + - -dependence f0f0 f2f2

31
1) Ross-Stodolsky B-W for 0 (770), f 0 (980) and f 2 (1270) with variable skewedness parameter, 2) ++ (1232) + - inv.mass spectrum and + - phase space. Background Subtraction

32
( * p p 0 ) vs W

33
d /dt ( * p p 0 ) Fit by e bt Large t min ! (1.6 GeV 2 )

34
Angular distribution analysis, cos cm Relying on SCHC (exp. check to the ~25% level)

35
Longitudinal cross section L ( * L p p L 0 )

36
Interpretation “a la Regge” : Laget model *p p 0 *p p *p p Free parameters: *Hadronic coupling constants: g MNN *Mass scales of EM FFs: (1+Q 2 / 2 ) -2

37
Regge/Laget L ( * L p p L 0 ) Pomeron ,f 2

38
VGG GPD model +

39
GK GPD model +

40
H, H, E, E (x,ξ,t) ~~ x+ξx-ξ t γ, π, ρ, ω… -2ξ x ξ-ξ-ξ +1 0 Quark distribution q q Distribution amplitude Antiquark distribution “ERBL” region“DGLAP” region W~1/ ERBLDGLAP

41
DDs + “(fitted) meson exchange” DDs w/o “meson exchange” (VGG) “(fitted) meson exchange”

42
Comparison of cross sections is model-dependent: k perp dependence ansatz, model for GPDs,… L / T ~Q 2 L ~1/Q 6 T ~1/Q 8 Q 2 dependence: Saturation with hard scale of b SCHC : checks with SDMEs J ~9/1/2/8 ~|xG(x)| 2 W (or x B ) dependence: Ratio of yields: Some signatures available for gluon handbag are not relevant for quark handbag: Model-independent features:

43
CLAS@6 GeV S. Morrow et al., Eur.Phys.J.A39:5-31,2009 ( 0 @5.75GeV)

44
b (from e bt ) as a function of Q 2 (be careful of correlation with W) L / T as a function of Q 2 (be careful of correlation with W)

45
Exclusive electroproduction at CLAS12 CLAS12 proposal PR12-11-103 Q 2 range at 6 GeV Q 2 range at 12 GeV

47
decay angular distribution (polar angle cm ) CLAS12 proposal PR12-11-103 purely statistical error bars statistical error bars +10% systematic

48
Exclusive electroproduction

49
ep->ep

50
cos( cm ) distribution cm distribution

51
Laget Regge model for *p p Cross section ( * p p Laget T + L Laget L VGG L (H&E) Issue with GPD approach if 0 exchange dominant : 0 ->E E subleading in handbag for VM production (GK includes 0 exchange with k perp effects) ~ ~ while DESY data CORNELL data

52
Cross section ( * p p Comparison with GPD calculation (VGG)

53
Exclusive + electroproduction (A. Fradi’s thesis) Slow but steady progress towards publication ! towards publication !

54
++ e - ) (p) One event in CLAS e p e’ [n] e’ [n] + 0 e’ [n] Channel selection IC EC

55
Invariant mass IM( + 0 )

56
Invariant mass IM(n 0 ) Invariant mass IM(n + )

57
Invariant mass IM( + 0 )

58
PRELIMINARY Total cross section Q 2,x B ) +

59
Laget Regge “hadronic” approach Laget Regge “hadronic” approach + ++ ++ ++ n ++ n GPD “partonic” approach GPD “partonic” approach +L+L H, E ρ0ρ0ρ0ρ0 e u H u - e d H d e u E u - e d E d e u H u + e d H d e u E u + e d E d ρ+ρ+ρ+ρ+ H u - H d E u - E d

60
“Hadronic approach”: Laget model ++ 00

61
“Hadronic approach” Laget model does not reproduce the drop of d /dt for t →0 PRELIMINARY

62
(*) “Partonic approach”: GPDs GPDs 00 VGG GPD model GK GPD model ++ GPDs p n LL e e’e’

63
GPDs model agrees fairly with the data at low x B (high W) GPDs model misses the data at high x B (low W) (*) “Partonic approach”: GPDs Only H in this calculation

64
(*) Hint of GPD E dominance The GPD E reproduces the drop of d /dt for t →0

65
L. Morand et al., Eur.Phys.J.A24:445-458,2005 ( @5.75GeV) C. Hadjidakis et al., Phys.Lett.B605:256-264,2005 ( 0 @4.2 GeV) K. Lukashin, Phys.Rev.C63:065205,2001 ( @4.2 GeV) J. Santoro et al., Phys.Rev.C78:025210,2008 ( @5.75GeV) S. Morrow et al., Eur.Phys.J.A39:5-31,2009 ( 0 @5.75GeV) A. Fradi, Orsay Univ. PhD thesis, 2009 ( @5.75GeV) (preliminary)

66
Comparison of t-slope for channels at 6 GeV

67
VMs ( 0, ) the only exclusive process [with DVCS] measured over a W range of 2 orders of magnitude ( L,T, d /dt, SDMEs,…) At low energy (W<5 GeV), success of “hard” approach for the channel ( nucleon gluon imaging) but large failure for the 0, + channels. This is not understood. Why the GPD/handbag approach sould set at much larger Q 2 for valence quarks ? Are the widely used GPD parametrisations in the valence region completely wrong ? JLab12 PR12-11-103 proposal: broader phase space, check when Q 2 independence settles for a variety of observables At high energy (W>5 GeV), transition from “soft” to “hard” ( 2 scale) physics relatively well understood (further work needed for precision understanding/extractions) handbag interpretation and nucleon imaging handbag interpretation and nucleon imaging

68
W~1/ GPDs/handbag GPDs/handbag ???

69
BACKUP SLIDES

70
H, H, E, E (x,ξ,t) ~~ x+ξx-ξ t γ, π, ρ, ω… -2ξ x ξ-ξ-ξ +1 0 Quark distribution q q Distribution amplitude Antiquark distribution “ERBL” region“DGLAP” region W~1/ ERBLDGLAP

71
DDs + “meson exchange” DDs w/o “meson exchange” (VGG) “meson exchange”

72
( * p p 0 ) vs W

73
Regge/Laget L ( * L p p L 0 ) Pomeron ,f 2

74
Exclusive electroproduction

75
ep->ep

76
GK L LL Laget T + L W=2.9 GeV W=2.45 GeV W=2.1 GeV

77
100% acceptance & integrated over all variables but (x B,Q 2 ) 6 GeV e fixed p target Counting rates for 1000 hours at 10 34 cm -2 s -1 Limitation comes from phase space

78
100% acceptance & integrated over all variables but (x B,Q 2 ) 6 GeV e fixed p target Counting rates for 100 hours at 10 34 cm -2 s -1 Limitation comes from phase space

79
100% acceptance & integrated over all variables but (x B,Q 2 ) 11 GeV e fixed p target Counting rates for 1000 hours at 10 35 cm -2 s -1 Limitation comes from phase space

80
100% acceptance & integrated over all variables but (x B,Q 2 ) 11 GeV e fixed p target Counting rates for 1000 hours at 10 35 cm -2 s -1 Limitation comes from phase space

81
100% acceptance & integrated over all variables but (x B,Q 2 ) Counting rates for 1000 hours at 10 34 cm -2 s -1 11 GeV e 60 GeV p Limitation comes from luminosity

82
100% acceptance & integrated over all variables but (x B,Q 2 ) Counting rates for 1000 hours at 10 34 cm -2 s -1 11 GeV e 60 GeV p Limitation comes from luminosity

84
6 GeV e fixed p target 11 GeV e fixed p target 11 GeV e 60 GeV p

85
d /dt ( * p p 0 ) Fit by e bt Large t min ! (1.6 GeV 2 )

86
L ( L ( b d L dt ( d L dt ( b Longitudinal cross sections PRELIMINARY

87
e e Q ~ MeV Q >>GeV Increasing Q 2 : Q 2 >>

88
GPDs parametrization based on DDs (VGG/GK model) Strong power corrections… but seems to work at large W…

89
d /dt ( * p p 0 ) Fit by e bt Large t min ! (1.6 GeV 2 )

90
Steepening W slope as a function of Q 2 indicates « hard » regime (reflects gluon distribution in the proton) W dependence

91
Two ways to set a « hard » scale: *large Q 2 *mass of produced VM W dependence Steepening W slope as a function of Q 2 indicates « hard » regime (reflects gluon distribution in the proton) Universality : at large Q 2 +M V 2 similar to J/

92
P (0) increases from “soft” (~1.1) to “hard” (~1.3) as a function of scale 2 =(Q 2 +M V 2 )/4. Hardening of W distributions with 2

93
Approaching handbag prediction of n=6 (Q 2 not asymptotic, fixed W vs fixed x B, tot vs L, Q 2 evolution of G(x)…) Q 2 dependence L ~ /Q 6 => Fit with ~1/(Q 2 +M V 2 ) n Q 2 >0 GeV 2 => n=2+/- 0.01 Q 2 >10 GeV 2 => n=2.5+/- 0.02 Q 2 >0 GeV 2 => n=2.486 +/- 0.08 +/-0.068 J (S. Kananov) Q 2 dependence is damped at low Q 2 and steepens at large Q 2

94
t dependence b decreases from “soft” (~10 GeV -2 ) to “hard” (~4-5 GeV -2 ) as a function of scale 2 =(Q 2 +M V 2 )/4

95
Ratios J ~ 9/1/2/8 1/sqrt(2){|uu>-|dd>} 1/sqrt(2){|uu>+|dd>} Ratio =9

96
L/TL/TL/TL/T (almost) compatible with handbag prediction (damping at large Q 2 )

97
SDMEs HERMES H1 (almost) no SCHC violation

98
HERMES Cornell CLAS

99
LL ep->ep GK L CLAS HERMES HERA

100
Exclusive electroproduction: gluon imaging of the proton x<0.01: measured at H1/ZEUS x>0.1: practically unknown: with CLAS12

101
(A. Kubarovsky’s simulations) Extract t–slope of d L /dt up to Q 2 ~7 GeV2 As a function of Q 2 : check when Q 2 -independence settles As a function of x B (or W): first 3D-gluon imaging at large x Exclusive electroproduction: gluon imaging of the proton CLAS12 proposal PR12-11-103:

102
C. Weiss:

103
LO (w/o kperp effect) Handbag diagram calculation needs k perp effects to account for preasymptotic effects LO (with kperp effect) Same thing for 2-gluon exchange process

Similar presentations

OK

Hard Exclusive Pseudo-Scalar Meson Production in CLAS Valery Kubarovsky Jefferson Lab Partons in Nucleons and Nuclei Marrakech, Morocco, September 26-30,

Hard Exclusive Pseudo-Scalar Meson Production in CLAS Valery Kubarovsky Jefferson Lab Partons in Nucleons and Nuclei Marrakech, Morocco, September 26-30,

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Maths ppt on surface area and volume class 9 Download ppt on nationalism in indochina Themes free download ppt on pollution Ppt on hcl company profile Ppt on network theory pdf Ppt on network theory definition Ppt on condition monitoring training Ppt on finite difference method Ppt on campus recruitment system online Ppt on group development wheel