Low-­‐mass	
  di-­‐leptons	
  	
  
in	
  J-­‐PRAC	  E16	K.	
  Ozawa	
  (KEK)	
  Contents	
• J-­‐PARC	
  and	  Hadron	
  Experimental	
  Facility	  • Di-­‐electron	  measurements	
  @	  J-­‐PARC	  	
  – Vector	
  meson	
  mass	  spectra	
  in	
  nucleus	  • Further	
  possibility	
  in	
  pA	
  mesurements	

2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	  	2	

100km	J-­‐PARC	KEK	
Tsukuba	
  Univ.	

CERN	Tokyo	
10000km	
Tsukuba	

2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	  	3	J-PARC

Tokai, Japan(Japan Proton Accelerator Research Complex)
Material and Life Science
Facility

400 MeV Linac

RCS
3 GeV Synchrotron 	 MR
30 GeV Synchrotron

Hadron Experimental
FacilityHall
Hadron60m x 56m
Neutrino Experimental
Facility

2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

4	
  

30	
  GeV	
  Accelerator	
  &	
  	
  
Hadron	
  Experimental	
  Facility	
r	
  	
  	

rato
	
  Accele

ton

	
  pro
V
e
G
0
3

Hadron	
  Experimental	
  Facility	
Transfer	  Line	  from	
  
Acc.	
  to	
  Hadron	New	
  Beamline	  (under	  construc6on)	

Current	
  Produc[on	
  target	  for	
  secondary	
  beams	
  	

Branch	  Point	
  from	
  
Acc.	
  to	
  Hadron	
2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	  	

5	

HadronExperimental Facility
K1.8
K1.8BR

K1.1

KL
High-p
COMET

Name	
 
Species	 Energy	
  	
 
K1.8	
 
π±,	
  K±	
 
<	
  2.0	
  GeV/c	
 K1.8BR	
 
π±,	
  K±	
 
<	
  1.0	
  GeV/c	
 
K1.1	
 
π±,	
  K±	
 
<	
  1.1	
  GeV/c	 proton	 30GeV	
 High-­‐p	 Unseparated	 <	
  20GeV/c	
 2015/3/13	

Intensity	
 
~105	
  Hz	
  for	  K+	 ~	
  104	  Hz	  for	  K+	 ~	
  104	  Hz	  for	  K+	 ~	
  1010	
  Hz	
 

K.	
  Ozawa,	
  CiRfSE	
  workshop	  	~	
  108	  Hz	 Under	
  Construc[on	
6	

QCD	
  medium	

Temperature	
  T	

QCD:	
  Quantum	  Chromo	  Dynamics	

LHC/RHIC	
  K.	
  Fukushima	
  and	  T.	
  Hatsuda,	
  Rep.	
  Prog.	
  Phys.	
  74	
  (2011)	
  014001	

Nucleus	Free	
  Space	

Nucleus	
  is	
  a	
  stable	
  and	
  dense	  ma9er!	

2015/3/13	

Baryon	  Chemical	
  Poten[al	
  µB	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

7	Hadron and QCD medium	
mesons	•baryons	

Hadron mass isunderstood a sum of
constituent quark masses

Mass [GeV]– Dynamical mass•

The fact that π meson has
a “too light” mass (Mπ ~130 MeV/c2 ) is
understood as NG bosonof chiral symmetry
breaking.

•

In fact, chiral symmetryis broken in the realworld.

Constituent
quark mass
Pseudo Scalarmeson as NG
boson（Jp=0-）	

masses of chiral partners
are different.
– ρ (JP = 1-) m=770 MeV
a1 (JP = 1+) m=1250 MeV–

2015/3/13	

K. Ozawa, CiRfSE workshop 	8	

QCD phase and <qq>	< qq >≈ 250MeVØSpontaneous breaking ofa symmetry is marked by:* a non-zero orderparameter, the quark
condensate <qq> inthe case of QCD

heavy ion reactions:
A+A→V+X
mV(ρ>>ρ0;T>>0)< qq >≈ 0

3

High T
High ρ	

At Nuclear Densityγ, π. p - beams

SPS

J-PARC elementary reaction:
LEPS2γ, p, π → V+X

mV(ρ=ρ0;T=0)

RHIC
LHC
2015/3/13

K. Ozawa, CiRfSE workshop

We can study medium property as functions of T and ρ.	

9	Observables
	However, the quark condensate is not an observable and one need tofind observables which are related to the quark condensate.
We need to find out observables related to quark condensates.
Relations between mass spectra of V-AV mesons and condensates isdeveloped using a sum rule.
Hatsuda, Koike and Lee, Nucl. Phys. B394 (1993) 221
Kapusta and Shuryak, Phys. Rev. D49 (1994) 4694

In free space, there is a good measurement done by ALEPH group.
（ALEPH, Phys. Rep. 421(2005) 191） See the next slide.
2015/3/13

K. Ozawa, CiRfSE workshop

10Condensates and spectra	
ALEPH, Phys. Rep. 421(2005) 191	

2015/3/13	

K. Ozawa, CiRfSE workshop 	

11	

QCD Sum rule	Measurements of axial vector mesons in a medium is difficult.
Different type of sum rule is proposed.	

Vacuum	q	

Vacuum	q	

QCD sum rule	

Average of Imaginary
part of Π(ω2)
vector meson
spectral function	

Example:	
Theoretical Assumption	

Prediction	

mV	

T.Hatsuda and S.H. Lee,PRC 46 (1992) R34

mV* ⎛ρ ⎞= ⎜⎜1 − α B ⎟⎟ ; α ≈ 0.03
mV ⎝
ρ0 ⎠

Spectrum	Measurements of vector mesons can be donein nucleus and high energy collisions.
2015/3/13

K. Ozawa, CiRfSE workshop

12NA60 Results @ SPS
Muon pair invariant mass in Pb-Pb at √sNN=19.6 GeV[van Hees+R. Rapp ‘06]

PRL 96, 162302 (2006)	

Mass spectra is reproduced by acalculation based on hadroninteraction.
Evaluation of condensates should bedone.
2015/3/13

K. Ozawa, CiRfSE workshop

13
13

HADES@GSI	G. Agakishiev et al. Eur.Phys.J. A 48 64 (2012).	

Proton beamenergy at 3.5 GeV	Enhancement both for
p+p and p+Nb?!	
They claim effects ofN* resonances.	
2015/3/13

K. Ozawa, CiRfSE workshop

14

In pA (KEK-PS E325)
	
12 GeV proton induced.
p+A → φ + X
Electrons from φ decays are detected. 	

βγ<1.25 (Slow)

Decays outside nucleus	

R. Muto et al., PRL 98(2007) 042581
Decays inside nucleus	

Cu

φmeson has NOmass modification
Blue line shows
expected line shapeincluding all
experimental effects
wo mass modification

φmeson has
mass
modification

e+e- invariant mass	

Modification isshown as an
Excess	

Indication of mass modification! 	
2015/3/13	

K. Ozawa, CiRfSE workshop

15	Target/Momentum dep.
βγ<1.25 (Slow)

1.25<βγ<1.75

Two nuclear targets:
Carbon & Copper
Inside-decay
increases in large
nucleus
Momentum bin
Slowly moving φmesons havelarger chance todecay inside nucleus	

Excess	

2015/3/13	

Only one momentum
bin shows a massmodification under thecurrent statistics.

Same aspreviousslide	

K. Ozawa, CiRfSE workshop 	

e+e- invariant mass	

To see clear massmodification,
significantly larger
statistics are required.
16

New	
  Goal	  @	
  J-­‐PARC	
A	
  clear	
  shifed	
  peak	  needs	
  to	
  be	
  iden[ﬁed	
  to	
  establish	
  QCD-­‐originated	
  eﬀects	

Momentum	
  Dependence	

Pb	
E325	
  results	

2015/3/13	

Proton	

Extrapolate	17	
Target:	
  100	
  [mes	  larger	
  sta[s[cs	K.	
  Ozawa,	
  CiRfSE	
  workshop	  	

Experimental	
  set	
  up	Construct	
  a	
  new	
  beam	  line	  and	  new	
  spectrometer	
  Deliver	
  1010	
  per	
  spill	
  proton	
  beam	  	
  Primary	
  proton	
  (30GeV)	
  beam	
  	
  

Cope	
  with	  1010	
  per	
  spill	
  beam	  intensity	
  (x10)	
  Extended	
  acceptance	
  (90°	  in	  ver[cal)	
  (x5)	
  Increase	
  cross	
  sec[on	
  (x2)	
  New	
  high	  momentum	
  beam	  line	2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

18	

Further	
  physics	
  opportuni[es	• We	  are	
  planning	
  to	
  have	  hadron	
  iden[ﬁca[on	
  detectors	
  in	
  
the	
  spectrometer	
  to	
  extend	
  physics	
  opportuni[es.	
  • Cross	  over	  between	
  Quark	  and	  Hadron	  – Mul[-­‐hadron	
  produc[on	
  and	
  Correla[on	
  measurements	
  for	  several	  energies	
  and	
  reac[on	
  systems	
  are	
  important	  • Experimental	
  informa[on	
  of	
  Mul[-­‐hadron	
  produc[on	
  in	
  pp	
  and	  pA	  reac[ons	
  are	
  limited	
  	
  	
  

– Eﬀects	
  of	
  hadron-­‐hadron	
  interac[ons	
  	
  should	
  be	
  understood	  in	
  terms	  of	
  high	  energy	
  HI	
  physics.	
  	
  • When	  we	
  found	
  an	
  interes[ng	
  object	
  for	
  our	
  physics,	
  then	  we	
  should	
  
take	
  a	
  comprehensive	  data.	
  Then,	
  one	
  can	
  ﬁgure	
  out	
  what	  kind	  of	
  physics	
  have	  a	
  main	
  role	  in	
  our	
  data.	
  

• As	
  a	
  future	
  plan,	  heavy	
  ion	
  beam	  at	
  J-­‐PARC	
  is	
  under	  discussion.	
  	
  2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

19	

Aspects	
  of	
  hadron	
  physics	
These	
  aspects	
  are	
  strongly	
  related,	  especially	
  in	
  interpreta6ons	
  of	
  experimental	
  results	  	Interac[on	
  btw	
  “color-­‐less”	
  par[cles	

2015/3/13	

Inside	  Structure	

Hadron-­‐Hadron	
  Interac[on	

Building	  blocks?	
  Interac[on	
  btw	
  building-­‐blocks	  in	
  hadron	QCD	
  Phase	  Diagram	K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

QCD	
  medium	  and	
  hadron	
  proper[es	20	Summary	• J-­‐PARC	
  is	
  the	
  nearest	
  experimental	
  facility	
  for	
  hadron	
  physics.	
  	
  • Chiral	  proper[es	
  of	
  QCD	
  medium	  are	
  studied	
  using	
  measurements	
  of	
  vector	
  meson	
  mass	  spectra.	
  	
  • Several	
  measurements	
  are	
  already	
  done	  using	
  AA	
  and	  pA	  collisions	  to	
  inves[gate	
  high	  temperature	  or	
  high	  density	
  mapers.	
  • Results	
  show	
  modiﬁca[ons	
  of	
  mass	  spectra.	
  To	
  study	  more	  details	
  of	
  chiral	  proper[es,	  higher	
  sta[s[cs	
  	
  and	
  beper	  resolu[on.	
  Such	  experiments	
  will	  be	
  done	  at	  J-­‐PARC.	

2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

21	

BACKUPS	

2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

22	

QCD	
  Lagrangian	Gluon	

Chiral	  symmetry	
quark	

Divide	  with	  chirality	  Neglect	
  
mass	
(if	
  m	
  ~0)	V(q)	The	
  lagrangian	  does	  not	
  change	
  under	  the	
  transforma[on	
  below.	

This	
  symmetry	
  is	
  called	  	
  Chiral	
  symmetry.	
2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	  	
  Symmetric	  in	
  rota6on	

q	
23	
  

Breaking	
  
o
f	
  
s
ymmetry	When	
  the	
  poten6al	
  is	
  like	  V(φ)	
  =	
  φ4,	
Poten[al	
  is	
  symmetric	
  and	
  Ground	  state	  (vacuum)	
  is	
  at	
  symmetric	
  posi[on	
  	If	
  the	
  interac6on	
  generate	
  addi6onal	
  poten6al	
  automa6cally,	  V’(φ)	  =	  -­‐a*φ2	
Poten[al	
  is	
  s[ll	  symmetric,	
  however,	
  Ground	  state	  (vacuum)	
  is	
  at	
  non-­‐symmetric	
  posi[on	
  	
This	
  phenomenon	
  is	
  called	  	
  spontaneous	  symmetry	
  breaking	

δV	
  	
  
~	
  self	  energy	
  of	
  ground	
  state	  ~	
  mass	
2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

24	
  

In	
  QCD	High	
  Temperature	  High	
  Density	
Chiral	  symmetry	  exists.	
  
Mass	
  ~	
  0	
  (Higgs	
  only)	

When	
  T	
  and	
  ρ	
  is	
  
going	
  down,	Vacuum	Quark	  –	  an[quark	
  pairs	
  make	  a	  condensate	
  and	
  give	  a	
  poten[al.	
  Chiral	  symmetry	
  is	
  breaking,	
  spontaneously.	

q	

Vacuum	q	

Vacuum	  contains	
  quark	  an[quark	
  condensates.	
  So	
  called	
  “QCD	  vacuum”.	
  

π	
  as	
  a	
  Nambu-­‐Goldstone	
  oson.	
  
	
 	
  
K.	
  Ozawa,	
  b
CiRfSE	  workshop	
  2015/3/13	
  

25	
  

How	
  to	
  study	  more	  details?	
“QCD	
  medium”,	
  i.e.	
  quark	
  condensates	
  
can	
  be	
  changed	
  in	
  ﬁnite	  density	  or	  temperature	
  maper.	
  Then,	
  chiral	  symmetry	
  will	
  	
  	
  	
  	
  be	
  
restored	  (par[ally).	
  Vacuum	
  
ρ	
  ≈	
  0	
In	
  ﬁnite	  ρ/Τ	  	

Chiral	  proper6es	
  can	  be	
  studied	
  	
  
at	
  ﬁnite	  density	
  or	
  temperature.	
  	
  Nucleus	
  can	  be	
  used	  as	
  a	
  ﬁnite	  density	
  system.	
  High	
  energy	  heavy	
  ion	  collisions	
  can	
  generate	
  	
  
a	
  high	  temperature	
  ma9er	Chiral	  property	
  of	
  the	
  medium	
  is	
  characterized	
  by	
  a	
  quark	
  condensate.	
  The	
  quark	
  condensate	
  is	
  an	
  order	  parameter	
  of	
  chiral	  symmetry.	
  	
  2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

26	
  

INS-­‐ES	  	
  TAGX	
  experiment	  	
  Eγ~0.8-­‐1.12.GeV,	
  sub/near-­‐threshold	
  ρ0	
  	
  produc6on	
  
•
•
•

PRL80(1998)241,PRC60:025203,1999.:	
  	
  mass	  reduced	
  in	
  invariant	
  mass	  spectra	  of	
  3He(γ,	
  ρ0)X	  ,ρ0	  -­‐-­‐>	
  π+π−	  Phys.Le9.B528:65-­‐72,2002:	
  introduced	
  cosθ	  analysis	
  to	
  quan6fy	
  the	
  strength	
  of	
  
rho	
  like	  excita6on	  	
  Phys.Rev.C68:065202,2003.	
  In-­‐medium	  ρ0	
  spectral	
  func6on	
  study	  via	  the	
  H-­‐2,	
  He-­‐3,	  C-­‐12	
  (γ,π+	
  π-­‐)	
  reac6on.	
  	
  

Try	
  many	  models,	
  and	
  channels	
  
	
  Δ,	
  N*,	
  3π,…	  2015/3/13	
  Eγ

STT model
Present
work

Previouswork

800-960
MeV

700-710MeV

672±31
MeV

960-1120
MeV

730
MeV

743±17
MeVK.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

27	
  

CLAS	
  g7a	  @	
  J-­‐Lab	

Induce	  	
  photons	
  to	
  Liquid	
  dueterium,	
  Carbon,	
  Titanium	
  and	
  Iron	  	
  targets,	
  generate	
  vector	  mesons,	
  and	
  detect	
  e+e-­‐	  decays	
  with	  large	  acceptance	
  spectrometer.	
  
R. Nasseripour et al., PRL 99 (2007) 262302

γ

ω/ρ/φ

No	
  peak	  shif	
  of	
  ρ	
  	
  
Only	
  broadening	
  is	
  observed	  2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	  	
  mρ = m0 (1 - α ρ/ρ0)for α = 0.02 ± 0.02

28	  

Mass	
  spectra	
  measurements	
  KEK	
  E325,	
  ρ/ω → e+e-­‐	  	

Induce	  12	
  GeV	
  protons	
  to	
  Carbon	  and	
  Cupper	
  target,	
  generate	
  vector	
  mesons,	
  and	
  detect	  e+e-­‐	  decays	
  with	  large	  acceptance	
  spectrometer.	
  
M. Naruki et al., PRL 96 (2006) 092301

ω/ρ/φ
Cu	
  	
  	
  

ρàe+e-ωàe+e-The	
  excess	
  over	  the	
  known	
  hadronic	
  sources	
  on	
  the	
  low	  mass	
  side	  of	  ω	  peak	  has	  been	  observed.	
  mρ = m0 (1 - α ρ/ρ0) for α = 0.09

2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

29	
  

Results	
  from	  CBELSA/TAPS	  TAPS,	  ω	  →	
  π0γ	
  with	  γ+A	pγ

arXiv:	
  1005.5694	
  

γ
ω

π0

γ

mω =
advantage:

γA → ω + X
π 0γ

γ

γγ
	

(pπ + p γ )2

• π0γ large branching ratio (8 %)• no ρ-contribution (ρ → π0γ : 7 ⋅ 10-4)
disadvantage:• π0-rescattering
2015/3/13	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

30	
  

Deeply bound π	Large overlap of wave function	

Sensitive to π-nucleus strong
interaction potential	

Measure binding energy canbe converted to this b1
information	
2015/3/13

K. Ozawa, CiRfSE workshop

31

Exp. Results
K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302	

π bound state is observed inSn(d, 3He) pion transfer reaction at GSI.
Reduction of the chiral order parameter,f*π(ρ)2/fπ2=0.64 at the normal
nuclear density (ρ = ρ0 ) is indicated.	

Experiment is
continued at RIKEN
and positive results
are alreadyobtained.	

2015/3/13

K. Ozawa, CiRfSE workshop

32

Current status of experiments
	
Most measurements are done for ρ/ω mesons	• High energy heavy ion collisions– SPS-NA60 (PRL 96 (2006) 162302)• Modification of ρ meson due to hadronic effects– RHIC-PHENIX (PRC81(2010) 034911)• Origin of the enhancement is under discussion• Nuclear targets– CBELSA/TAPS (Phys.Rev. C82 (2010) 035209)• Modification of ω is not observed

Large• Mass broadening of ρ due to hadronic effects
uncertaint– KEK-PS E325 (PRL 96 (2006) 092301)
y in• Peak shift and width broadening of ρ/ω
backgroundsubtractio
Several hadronicandnmethod	2015/3/13	
33	
K. Ozawa, CiRfSE workshop 	– J-LAB CLAS G7 (PRL 99 (2007) 262302)

experimental effects cause

How about φ meson?
	• ρ/ω

– Dynamical mass contribution is dominantMπ ~ 130 MeV/c2

Mρ ~ 770 MeV/c2– Large hadronic effects and background issues are
large

• φ

– Still, dynamical mass contribution is dominantMη ~ 550 MeV/c2

Mφ ~ 1020 MeV/c2– Narrow width ( 4.3 MeV/c2)• Small background issue– Small effects of hadron-hadron interactions• e.g. Binding energy of φN is 1.8 MeV (Phys. Rev. C 63(2001)
022201R)

To see QCD-originated effects, φ meson is the most promi
2015/3/13	

K. Ozawa, CiRfSE workshop 	

34	Experimental Setup
12 GeV proton induced.
p+A → φ + X
Electrons from φ decays are detected. 	

KEK E325	

2015/3/13

K. Ozawa, CiRfSE workshop

35

E325 Spectrometer

2015/3/13

K. Ozawa, CiRfSE workshop

36

Next step	Evaluate quark condensate directly.	
Replace by average
Average of Imaginary part of Π(ω2)	
 of measured spectra	

Assumed Spectrum	p	Then, calculate quark condensate
using QCD sum rule.
	Experimental
1. High statics
requirements 	
 2. Good mass resolution	
2015/3/13

K. Ozawa, CiRfSE workshop

37

What can be achieved?
Pbφφ

Modified φ
φ

φ

φ

φ φ φ
φ
φ fromProton[GeV/c2]Highresolution	
Invariantmass inmedium2015/3/13

Ozawa, CiRfSE workshop
Dispersion K.
relation	

38

Calc.	
  with	  other	  models	
βγ<0.5E325
Δm : 35 MeV(28 ~ 41)
Γ : 15 MeV(10~23)cf.	
  Hatsuda,	
  Lee	  (PRC46,	
  34)	
  
Δm	
  :	
  	
  12~44	
  MeV	
  	
  	
  	
  	
  
Γ	
  	
  	
  :	
  	
  	
  not	
  es[mated	
  	

--Δm : 35 MeV
Γ : 50 MeVCu	  0.5<βγ<1.25

βγ<0.50.5<βγ<1.25

Oset, Ramos(NPA 679, 616)
Δm : 10 MeV
Γ : 15 MeV

Hadronic	
  model	

Pb	
  

Cu	
  

Klingle, Waas,
Weise(PLB431,254)
Δm : 10 MeV
Γ : 50 MeV

Hadronic	
  model	Pb	
  blue:	
  decays	
  inside	
  nuclei	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  red:	
  decays	
  outside	
  nuclei	
  Ozawa,	
  CiRfSE	
  workshop	
  	
39	
At	
  2015/3/13	
J-­‐PARC,	
  clear	
  mass	  spectra	
  in	
  nK.	
  ucleus	
  
will	
  be	
  obtained	
  to	
  compare	  with	  models.	

① GEM foil		
  D
evelop	
  1	
  detector	
  unit	
  and	
  make	  26	
  units.	
R&D	
  Items	
② GEM Tracker	

CsI	
  +	
  GEM	
  photo-­‐cathode	
  

50cm	
  gas(CF4)	
  radiator	
  
~	
  32	
  p.e.	
  expected	
  CF4	
  also	
  for	
  mul[plica[on	
  in	
  
GEM	

Ioniza[on	
  (Drif	  gap)	
  +	
  Mul[plica[on	
  (GEM)	
  High	
  rate	  capability	
  	
  

+	
  2D	
  strip	
  readout	
2015/3/13	
  ③ Hadron Blind detector	
K.	
  Ozawa,	
  CiRfSE	
  workshop	  	
  Gas Cherenkov for electron-ID	

40	  Detector	
  components	
Tracker	  ~Posi[on	
  resolu[on	
  100μm	
High	
  Rate(5kHz/mm2)	
  Small	  radia[on	
  length	
  (~0.1%	
  per	  1	
  chamber)	
  
	
  
	
  

2015/3/13	
  

	
  
	
  
Electron	
  iden[ﬁca[on	
  Large	
  acceptance	
  High	
  pion	  rejec[on	
  @	
  90%	  e-­‐eﬀ.	
  
100	
  @	
  Gas	
  Cherenkov	
  
25	
  @	
  EMCal	
  K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	
  

41	
  

Beam test results of prototype detectors (2012)
GEM
Tracker

100x100 200x200
Required position
resolution (~100µm) is
achieved

300x300

HBD (Hadron-Blind Cherenkov
detector )UV Cherenkov
photons aredetected with
CsI-evaporated
LCP-GEM
and CF4 gas

QE upto 40%

10 p.e.

Large	
  size	  (300x300mm)	
  PI-­‐	  and	  LCP-­‐GEM	
  are	  successfully	
  worked	
  for	  a	
  electron	
  beam	  – Stability	
  and	  response	  	
  for	  a	
  pion	  beam	  should	
  be	
  checked	
  at	  J-­‐PARC.	
  
●
GEM	
  Tracker	
  is	
  successfully	
  worked.	
  	
  ●Improvement	
  of	
  the	
  photo-­‐detec[on	
  eﬃciency	
  of	
  HBD	  is	
  on	
  going.	
  ●2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	
  	

42	

GEM Tracker : first prod. type is tested
islands for Y.Komatsu, NIM A 732(2013)241
Y-strip(Ni plated)

Y-strip

100m
m

200µm

X-strip 125µm(Ni plated)

x islandY
2015/3/13	

BVH type
2DCiRfSE	
  
R/O
PCB
K.	
  Ozawa,	  workshop	
  
	

43	

HBD	
  @	
  J-­‐PARC	
Electron	

2015/3/13	
  Ozawa,	
  CiRfSE	
  workshop	  	
  Cerenkov	
  blob,	
  φ	
  K.	
  
~34mm	44	  

	  HBD	  (Hadron	
  Blind	
  Detector)	
  	
  
●

Test	
  @	
  J-­‐PARC	
  K1.1BR	
  	
  in	
  2013/Jan	
  (T47)	
  ● pion	  rejec[on	
  is	
  	
  improved	
  with	  a	
  higher	  gain	  of	
  new	
  PI-­‐GEM	
  and	  	
  smaller-­‐size	
  readout	
  pad	  – measure	
  the	  distributed	
  charge:	
  selec[ng	
  3	
  ﬁred	  pads	  or	
  more	  •→	
  pion	  rejec[on	
  factor	
  100	
  with	  e-­‐eﬃciency	
  70%	  	
  achieved,	
  same	  level	  as	
  PHENIX,	
  in	
  spite	  of	
  the	
  less	
  #p.e.	
  e-eff. 70%
rejection>100

2015/3/13	

K.	
  Ozawa,	
  CiRfSE	
  workshop	  	45