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 :
- Usability for LVL1 trigger?
- Reaction plane reconstruction
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. or readout electronics ?
AGeV, Sep 2010
Z <ADC> <ADC>ratio Z2-ratio
of peak n/(n-1) (Z(n))2/(Z(n-1))2
Cell 35
/1 =4.00
/4 =2.25
/9 =1.77
/16=1.56
/25=1.44
Cell 168
/1 =4.00
/4 =2.25
/9 =1.77
/16=1.56
Cell 297
/1 =4.00
Small
cells
/1=4.00
/4=2.25
/9=1.77
/KaoS/ Ph.D. Thesis of A.Taranenko, 2001.
Lin-Y
Problems with
PMT gain
saturation
or readout electronics ?
ADC
Log-Y
Z=1
Z=2
Z=3
Z=4
Z=5
Z=6
ADC

5. Typical time spectrum:
AGeV, Sep 2010, cell 35
Typical time spectrum:
two-peak structure
observed
dN/d(ADC) from
1st time peak
spectators with Z=2,3,4
ADC
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 ? Z3
Time [ns]
ADC
Time [ns]
Time walk: different response
for particles with different Z
time
threshold
t3t2 t1
ADC Z3 Z2 Z1 t0
Z3 > Z2 > Z1
t3 < t2 < t1
ADC

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

10. 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

11. 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:

12. 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 centrality
selection in off-line analysis.
dN/db
b [fm]

13. Centrality trigger with TOF and FW ?
Centrality selection with multiplicity conditions in FW / TOF
dN/db
Mult(TOF)
is preferable
for LVL1
b [fm]

14. 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

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

16. 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

17. Backup slides/discussion

18. Structure of FW with 288 counters

19. Ni+Ni@1.25 AGeV, Sep 2010 PMT 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
KaoS: Ph.D. A.Taranenko (small, ѳ~0.7o)
peak ADC
Lin-Y
PMT gain
saturation
ADC
Log-Y
ADC

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

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

22. 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.

23. 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.

24. 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

25. 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

26. 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)

27. 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)