The Graal collaboration

09/10/2005 NSTAR2005 - Graal collaboration 1

The Graal collaborationresults and prospects

Presented by

Carlo SchaerfUniversità di Roma “Tor Vergata” and INFN - Sezione Roma II

for the Graal collaboration

NSTAR 2005 INTERNATIONAL WORKSHOP

ON THE PHYSICS OF EXCITED BARYONS12 - 15 October 2005, Tallahassee, Florida USA


Ladon beams in the world

Graal:

E = 0.6-1.5 GeV / W=1.4-1.9 GeV

Region of the second and third baryon resonances

, K, ’ thresholds

Complementarity of HIGS, LEGS, Graal and LEPS

’ threshold

threshold

K threshold

LEGS/BNL LEPS/SPRING8

(b)

threshold

GRAAL/ESRF

HIGS/FEL/DukeE (GeV)


Ladon beams in the world TABLE I Ladon Beams in the World

Project name Ladon° Taladon+ ROKK∆-1M LEGS* LEGS-2 Graal** LEPS† HIGS⊕

ocation Fracati (NF-INFN) Novoibirk Brookaven (BN) Grenoble Haria Dura

Storae rin Adone Adone VE PP-4M NSS NSS ESRF SPrin-8 TUNL -FELL

Enery definin etod colliation internal tain

tain external tain

external tain

internal tain

internal tain

colliation

Electron enery GeV 1.5 1.5 1.4 - 5.3 2.5 2.8 6.04 8 1.0

Poton enery eV 2.45 2.45 1.17-3.51 3.53 4.71 3.53 3.53 8.2

Gaa-ray enery MeV 5-80 35-80 100-1200 180-320 285-470 550-1470 1500-2400 5-225

variable iultaneou variable

Enery reolution % 1.4-10 5 -- 1.6 1.1 1.1 1.25 1

(FWHM) MeV 0.07-8 4-2 -- 5 5 16 30

Electron current A 0.1 0.1 0.1 0.2 0.2 0.2 0.1 100

Gaa intenity -1 105 5 105 2 106 4 106 2 106 2 106 2 106 106-108

Year of operation 1978 1989 1993 1987 1999 1996 1999

° Laer ADONe +TA ed LADON ∆ROKK i a ruian abbreviation for Backcattered Co pton Ga a * Laer Electron Ga a Source ** GRenoble Anneau Accelerateur Laer † aer-Electron Poton at SPrin-8 ⊕ Hi Intenity Ga a-ray Source.

, "r i v i er e d e Gr ece, au Pél op on n èse d ans l'A rc ad i e. . . . l es M yth ol ogis tes f ir en t l e Lad on p er e d e l a n ymph e Daphn é & d e l a n ymph e Syr in x . I l étoit cou vert d e magni f iqu es r oseau x , d on t Pan se ser vi t p our sa f lû te à sep t tu yau x . ” (M . Did er ot an d M . D'A l em ber t , Enc yc l op édi ,e a Par i s M DC CLV I )I


Ladon beam polarization

The first verification of the polarization of Ladon beams was performed at Frascati with the elastic scattering of the Ladon gamma-ray beam on the 15.1 MeV level of 12C using the small NaI crystal ball (7 x 16f ) of the University of Rome "La Sapienza". The experimental points reproduce very well the (1+cos2f) law expected for a fully polarized beam on a perfect polarization analyser.


Graal beam energyMaximum gamma-ray energies for E=6.04 GeV electrons

k1 z kmax Wmax xtag

E=6.04 GeV

nm

eV

4 k1

E

m2

GeV

GeV

mm

Nd YAG 1064.0 1.17 0.1083 0.590 1.410 17.32 Ar Ion Green 514.5 2.41 0.2230 1.101 1.717 35.67 Ar Ion G-B 488.0 2.54 0.2350 1.149 1.743 37.59 Ar Ion UV 351.1 3.53 0.3266 1.487 1.916 52.26 Ar Ion UV 320.0 3.87 0.3581 1.593 1.967 57.32 Ar Ion UV 300.0 4.13 0.3819 1.669 2.003 61.09 Nd Yag x 4 266.0 4.66 0.4312 1.820 2.073 69.00 Ar Ion G x 2 257.2 4.82 0.4460 1.863 2.092 71.36

Ar Ion G-B x 2 244.0 5.08 0.4700 1.931 2.122 75.19


Graal beam energy and thresholds

channel threshold (GeV) kmax (GeV) kmax- kth + p → + p 0.707 1.101 0.394

+ p→ ++ 0.911 1.149 0.238

+ p→ ++ 0 1.046 1.487 0.441

+ p→ + p 1.086 1.487 0.401 + p→ + p 1.108 1.487 0.379 + p→ + ' p 1.447 1.669 0.222 + p→ f 0+ p 1.492 1.669 0.177 + p→ + p 1.573 1.669 0.096


Graal beam polarization

Absolute value


Graal beam polarizationTheoretical linear polarization of

the -ray beam for two laser

lines: l =514 nm (green line)

and l =351 nm (UV line). The threshold energy of the tagging system is also shown

Green line UV line


The Graal Apparatus

Cross section of the BGO ball15 x 32=480

12

6

0

4

5

3

247

9

8

1413

12

11

10

3130

20

26

19

17

25

1816 15

22

23

21

2829

27


The Graal Experimental Program

We have enough data Results have been publishedand more are coming

Preliminary results are available but we want more data

We need more data and more efforts on the analysis

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r + p → π 0 + pr γ + n → π 0 + n

r γ + p →η + p

r γ + n →η + n

r γ + p → π + + n

r γ + p → K + + Λ

r γ + p → 2π 0 + p

r γ + p → K + + Σ0

r γ + n → K 0 + Λr γ + n → K + + Σ−

r γ + p → K 0 + Σ+

r γ + p → γ + p

r γ + n → γ + n


Time Of Flight resolutionTypical experimental Time Of Flight spectrum for the thin monitor versus the tagging counters. The distance between two

adjacent peaks is 2.8 ns corresponding to the distance between successive electron bunches. The timing

resolution is ≈ 0.3 ns (FWHM). The level of accidental coincidences in the main peak is less than 0.15%.

2.8 ns

≈ 0,3 ns


Two photon spectrum at the p0 mass

2 invariant mass spectrum around the p0 mass. Data (closed circles), before and after all kinematical cuts are applied, are compared with the simulation (solid line). The experimental width of the peak is ≈ 33 MeV (FWHM).

x 2≈ 33 MeV

FWHM


The azimuthal distribution in

Yields as a function of

for one value of and E:

a) Vertical polarization;b) Horizontal polarization;c) Sum of a and b;d) The ratio (a-b)/(a+b)

The solid line in d presents a fit of the type:

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nV −nH

nV +nH= Pγ Σ cos(2ϕ )

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r + p → π 0 + p


Green-UV data comparison

S

E=830 MeV E=865 MeV E=900 MeV

E=930 MeV E=965 MeV E=995 MeV

E=1025 MeV E=1055 MeV E=1090 MeV

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ϑp 0CM

Comparison of the data obtained with the Green laser line and the UV. The different laser lines produce -ray spectra with different intensities

and polarizations.

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r + p → π 0 + p


+ p p+ p0 S Asymmetry

• Graal o Erevan

SAID-FA04 Erevan S + Bonn dMAID2005 Bonn d + Graal SBonn2005 pN + N + K + KS + Graal S


+ p p+ p0 Differential cross section L.E.

• Graal * Bonn

SAID-FA04MAID2005Bonn2005


+ p p+ p0 Differential cross section H.E.

SAID-FA04MAID2005Bonn2005


Preliminary

+ p +(n) -> p°+ p +(n) Quasi-free proton (uv data)

Free proton

+p-> p°+p Said WI00 (free proton)GRAAL data are not included

Said FA01 (free proton)GRAAL data up to 1100 MeV are included

+ p +(n) -> p°+ p +(n) Quasi-free proton (green)

p° S for free and quasi-free proton


Error bars: only statistical errors

+ n +(p)->p0+n +(p)

Said (free neutron)Maid (free neutron)

Green Line

UV Line

Systematic errors <1.5%

po S for quasi free neutron 1/2 L. E.

Preliminary



+ n +(p)->p0+n +(p)

Said (free neutron)Maid (free neutron)

Green Line

UV Line

Systematic errors <1.5%

po S for quasi free neutron 1/2 H. E.

Preliminary


Quasi-free proton

Quasi-Free neutron

Preliminary

Comparison of beam asymmetry S for po photo-production on quasi-free proton and quasi-free

neutronlow energy bins


Quasi-free proton

Quasi-Free neutron

Comparison of beam asymmetry S for po photo-production on quasi-free proton and quasi-free

neutronhigh energy bins

Preliminary


59 MeVFWHM

Mass (GeV) Mass (GeV)

Mass after Cuts with simulation

after cuts

before kinematical cuts

from proton from neutron

invariant mass

€

+d → p + n +η


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N1 / K1

N1 / K1 + N2 / K2

=1

2• 1+ P Σ cos 2φ( )[ ]

f

+p+(n)->+p+(n)

+n+(p)->+n+(p)

Azimuthal Distribution:


S for the +p+(n)->+p+(n)


Said-BO12 Maid

S for quasi free proton: Gr vs UV Green Line

UV Line

Preliminary


cm (deg)

Preliminary

Said-BO12 (free proton)

Maid (free proton)

+ p + (n) -> + p + (n) Quasi-free proton

Free proton + p -> + p

S for free and quasi-

free proton


Comparison of S of photoproduction on

+p+(n)->+p+(n) Quasi-free proton

Quasi-Free neutron+n+(p)->+n+(p)

quasi-free proton and quasi-free neutron

Preliminary


Summary of resultsFirst results have been obtained on the analysis of the and po

photoproduction on the quasi-free proton and neutron on a deuteron target:differences in the behaviour start to appear at E=1 GeV.

Results show: photoproduction: qfp and free proton similar behavior

qfn and qfp similar behavior up to 1.2 GeV

po photoproduction: qfp and free proton similar behavior qfn and qfp different

behaviour at higher energy bins: NO change of sign for the neutron


Asymmetry S in +p K+

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p + π −

Preliminary


Asymmetry S in +p K++ S0

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↓+

↓p + π−

Preliminary


Polarization in +p K+

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↓p + π−

Preliminary


S Polarization in +p K+ S0

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+p + π −

Preliminary


Invariant mass:

n vs p. Neutron in Forward Detector

Preliminary


Invariant -n mass

(FD vs BGO)

Dashed Line Neutron in the

Forward Detectorn

Lab < 25°

Solid Line Neutron in the BGO n

Lab > 25° Preliminary

nLab < 25°

nLab > 25°


Vacuum-Assisted Photoionization


Green laser line

UV laser lines

A typical accuracy of 0.03 microstrip (= 9 ) is obtained for the position of a given line, corresponding to 0.2 MeV.

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Eγ max =4γ 2Elaser

1+4γ Elaser

me

≈ 4γ 2Elaser

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DEγ

Eγ

≈ 2 ⋅10−4;Δγ

γ≈

1

2

ΔEγ

Eγ

≈ 10−4

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=Ee

me

=6030

0.511=11 800; γ 2 ≈ 1.4 ⋅108

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Db =1

γ 2

⎛

⎝ ⎜

⎞

⎠ ⎟Δγ

γ≈ 10−8 ⋅10−4 ≈ 10−12

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d Eγ

Eγ

≈ 2dγ

γ; β dβ =

1

γ 2

⎛

⎝ ⎜

⎞

⎠ ⎟dγ

γ

Light Speed Anisotropy 1/5

Microstrip channels: 1 channel = 0.3 mm



Our “absolute” velocities

Rotation of the earth around its axis ≈ 0.32 km/s (Grenoble)

Revolution of the earth around the sun ≈ 30 km/s

Velocity of the Solar System in the Galaxy ≈ 215 km/s

Velocity of the Local Group of Galaxies ≈ 600 km/s

Motion relative to the Last Scattering Surface ≈ 370 km/s

(Velocity of light: c = 299 792 km/s)


Light Speed Anisotropy 3/50.1 div = 30 m


Light Speed Anisotropy 4/50.001 div = 0,3 m


The Graal beam line has been used also for some measurements of more fundamental physics. The most interesting result is a “Probe of the Light Speed Anisotropy With Respect to the Cosmic Microwave Background Radiation Dipole” . This measurement has been made possible by the high stability of the ESRF machine and the very good reproducibility of the Graal gamma-ray spectra. Many years of data have been used to plot the maximum gamma-ray energy as a function of the orientation of the Graal-ESRF interaction region with respect to the absolute direction of the Cosmic Microwave Background Radiation Dipole. Our result sets an upper limit on the anisotropy of the velocity of light of:

This limit is two-three orders of magnitude better than the one obtained from measurements involving space probes.

Mod. Phys. Lett. A 20, N. 1, 19-28 (2005)

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Dcc

≤ 3 ⋅10−12


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The Graal collaboration