1. HADES Collaboration meeting XXII,
FW status for the upcoming
HADES beam time
Alexander Sadovsky
Institute for Nuclear Research RAS,
Moscow
Readiness of FW to the physics run
Some results from Sep-2010 beam test
Simulation of :
- Reaction plane reconstruction
- LVL1 trigger usability?
HADES Collaboration meeting XXII,
May , 2011
Seillac, France

2. HADES Forward Wall, installed: March 2007
Fully operational: summer 2010
Distance to target 7m
140 small
64 middle cells
84 large 2

3. AGeV, Sep 2010

4. Ni+Ni@1.25 AGeV, Sep 2010 ADC gain saturation Small cell:35
ADC ratio Z2-ratio ratios ratio
n/(n-1) (Z(n))2/(Z(n-1))2 “(Z2/Z2)/(ADC/ADC)”
/1 =
/4 =
/9 =
/16=
/25=
/1 =
/4 =
/9 =
/16=
/1=
/1=
/4=
/9=
Small cell:35
peak ADC
Middle cell:168
Large cell:297
A.Taranenko (small, ѳ~0.7o )
peak ADC
Lin-Y
ADC gain
saturation
ADC
Log-Y
ADC

5. Ni+Ni@1.25 AGeV, Sep 2010, cell 35 dN/d(ADC) from 1st time peak
spectators with Z=2,3,4
ADC
Typical time spectrum
(two peaks)
dN/d(ADC) from
2nd time peak
spectators with Z=1,2,3
Time [ns]
ADC
Corresponding
spectrum of
ADC
dN/d(ADC) from tails
(slow particles)
mainly secondaries
ADC
ADC

6. Ni+Ni@1.25 AGeV, Sep 2010, cell 35 Trigger related ? Z1
Time [ns]
ADC
Time [ns]
Time walk: different response
for particles with different Z
time
threshold
t1t2 t3
ADC Z1 Z2 Z3 t0
Z1 > Z2 > Z3
t1 < t2 < t3
ADC

7. Ni+Ni@1.25 AGeV, Sep 2010, cell 35 Trigger selection of Mult(RPC)==2
Two peaks remain...
Time [ns]
{(Mult TOF + mult RPC )=2 && Mult TOF<1}

8. Conclusions: Simulations SHIELD Au+Au@1.25GeV 20k events by M.Golubeva
FW works, ready for data taking
Simulations
SHIELD 20k events by M.Golubeva
hGeant simulation with full reconstruction by K.Lapidus
hydra-8.21, hgeant-8.21, full HADES geometry
In simulation FW was placed on 5 meters from target
(in real data 7 meters)
No LVL1 emulation

9. Reconstruction of reaction plane
288 channels scintillator hodoscope located
5 m from the target
Reaction plane and centrality determination
⇉ K.Lapidus (CPOD-2010 at JINR)
Q > 6
Q > 3
No cut

10. Reaction plane reconstr.: Au+Au@1.25GeV/u
no selection
0 < b < 5
no weight
Z weight
5 < b < 10
10 < b < 15
43°
⇉ K.Lapidus (HADES coll.meet 2010, GSI)

11. FW fired cells distribution Au+Au@1.25AGeV
Selecting spectators
by peak at time-of-flight distrib. in FW cells
(left ): inside 2sigma
(right): outside2sigma
Spectators
Secondaries y y
100%
hits
x [cm]
x [cm]
16%
dN/dx
dN/dx
Time [ns]
Mean =18.1
Sigma=0.87
74%
x [cm]
Time [ns]
x [cm]

12. FW multiplicity vs. impact parameter
All hits:
no restriction on time-of-flight in FW cells
Spectators:
restriction on time-of-flight in FW cells

13. Number of fired FW cells (S,M,L) vs. b
Small size cells
Medium size cells
Large size cells b
secondaries (top)
spectators (bottom)
Restriction on time-of-flight at FW cells:

14. dN/db for different cut on num. fired cells
Increasing number of small
cells fired selects b~9
dN/db
b [fm]
Increasing number of medium
cells fired selects b~8
dN/db
b [fm]
Increasing number of large
cells fired selects b~6
This can be applicable for the off-line analysis.
dN/db
b [fm]

15. Centrality trigger with TOF and FW ?
Centrality selection with multiplicity conditions in FW / TOF
dN/db
b [fm]

16. Forward Wall team NPI Řež: INR Moscow: A.Kugler,
Yu.Sobolev JINR)
P.Tlusty,
V.Wagner.
INR Moscow:
O.Busygina,
F.Guber,
A.Ivashkin,
K.Lapidus Exc.Clust.Univ. & TU-Munich)
A.Reshetin,
A.Sadovsky,
E.Usenko.

17. Outlook Forward Wall was assembled and fully tested with real data
(2010) and ready for run.
Time- and amplitude- parameters of FW were studied.
FW response for the reaction was
simulated. Possibilities of the FW use for the reaction
plane reconstruction and it's potential usability in
LVL1 trigger were demonstrated.
Multiplicity in separate regions of FW (small, middle, large
cells) can be used in off-line analysis for an additional
centrality selection

18. Backup slides/discussion

19. Structure of FW with 288 counters

20. Ni+Ni@1.25 @ 1.25 AGeV, Sep 2010 Small cell 35 Middle cell 168
Peak
(n+1)/n
ratio (Z(n+1))2/(Zn)2
/1=4.00
/4=2.25
/9=1.77
/1=4.00
/4=2.25
/9=1.77
/1=4.00
9/4=2.25
/1=4.00
/4=2.25
/9=1.77
Small cell 35
peak mean-pedestal = charge
= 330
= 1030
= 1980
= 2540
Middle cell 168
= 690
= 2030
= 2650
Large cell 297
= 260
= 760
A.Taranenko (small, ѳ~0.7o )
peak charge

21. Ni + Ni @ 1.25 AGeV, Sep10 ADC: for all particles ADC:
22ns<Time<31ns
for spectators

22. Ni AGeV, Sep10
Time:
all hits
Time:
ADC Z=2

23. Reaction plane recons. : Au+Au@1.25GeV/u
Cut on Q value helps in suppression of tails and
improves the resolution
5 < b < 10
Q > 6
Q > 3
No cut
37o
⇉ K.Lapidus (HADES coll.meet. 2010, GSI)

24. Beam 0.9 AGeV, Jun10
Ni AGeV, Sep10

25. Multiplicities and immact param. distrib.
All hits, no restriction on time-of-flight in FW cells

26. Multiplicities and immact param. distrib.
Spectators hits:
restriction on time-of-flight in FW cells for spectators

27. dN/db for number of fired S, M, L cells
Small size cells
Medium size cells
Large size cells b
Dependence of number of fired cells (small, medium and large ones) from impact parameter. NB: “hill” of the distribution shifts
(no restriction on time-of-flight at FW cells).
One may see that large FW cells receive ~20 hits at b=0.

28. dN/db for number of fired S, M, L cells
Small size cells
Medium size cells
Large size cells b
Dependence of number of fired cells (small, medium and large ones) from impact parameter. NB: “hill” of the distribution shifts
(restriction on time-of-flight for spectators at FW cells ).
One may see that large FW cells receive ~8 hits at b=0.

29. M(tof), M(rpc) vs M(fw) at different b
Impact parameters range influence to M(tof+rpc) vs M(fw) and M(tof) vs M(fw): spectatrors only (Tfw)
dN/db b
dN/db b
dN/db b

30. M(tof), M(rpc) vs M(fw) at different b
Impact parameters range influence to M(tof+rpc) vs M(fw) and M(tof) vs M(fw): all particles
dN/db b
dN/db b
dN/db b

31. Ni+Ni@1.25 AGeV, Sep 2010 Small cell:35 Middle cell:168 Large cell:297
Lin-Y
Small cell:35
peak ADC
Middle cell:168
Large cell:297
A.Taranenko
(small, ѳ~0.7o )
peak ADC
ADC ratio Z2-ratio
(n+1)/n (Z(n+1))2/(Zn)2
/1=4.00
/4=2.25
/9=1.77
/1=4.00
/4=2.25
/9=1.77
/1=4.00
/1=4.00
/4=2.25
/9=1.77
ADC
Log-Y
ADC

32. FW cell: time dependence from particle Z
TRB module has different response for particles with
different Z
Z1 > Z2 > Z3
t1 < t2 < t3
time
threshold
t1t2 t3
ADC Z1 Z2 Z3 t0

33. Ni+Ni@1.25 AGeV, Sep 2010, cell 35 Time all Adc all Adc, time left
Adc, time right
Adc, time tail