1. Searching for Strange Quark Matter
with the CMS/CASTOR Detector at the LHC
P. Katsas, A.D. Panagiotou, E. Gladysz
for the CMS/CASTOR Group
CMS-HI meeting,

2. Outline Motivation: Unconventional Events in Cosmic Rays
Phenomenological Models & MC Simulations
“Strangelet” Identification Analysis
Summary

3. Hadron – Rich CR Events
Homogeneous thick lead chamber
Centauro
Normal

4. (Strangelet ?) 1.5 λI Hadron limit 3.6 λI 3.6 λI 3.2 λI Hadron limit
Measurement settings:
100 μm shower core diameter  threshold ~ 3 TeV
3.6 λI
Hadron limit
3.2 λI

5. Estimates for Centauro at LHC Centauro & Strangelet Generator
Energy density
ε ~ GeV/fm 3,
Temperature
T ~ MeV
Baryochemical potential
µb ~ GeV/fm3
CNGEN
Centauro & Strangelet Generator
anti- 
Phys. Rev. D45(1992)3134 Astroparticle Phys. 2(1994)167 Astroparticle Phys. 13(2000)173 Phys. Atom. Nucl. 67(2004)396

6. Multiplicity in CASTOR Acceptance
idpart
T = 250 MeV, q= 600MeV, ystop = 3.0
idpart
5.2 <  < 6.5
CENTAURO HIJING
Low multiplicity High multiplicity mostly baryons + kaons dominated by pions
Simulations - CNGEN

7. Probability of Centauro & Strangelet Detection
5.2<  < 6.5
CASTOR 
Estr (GeV) 
 = 9 GeV/fm3, T = 250 MeV, q= 330 MeV, ystop = 3.0
~ 60 % of Centauro decay products and ~ 10% of Strangelets within CASTOR acceptance

8. MC Radial Acceptance of CASTOR

9. Strangelets from Centauro Decay
5.2 <  < 6.5
Expected at LHC:
Energy densities up to є ~ 25 GeV/fm3
∆ystop ~
HIJING,VENUS
∆ystop ~ 2.3
BRAHMS-RHIC
 several to ~ 25% strangelets with energies E > 7 TeV, sufficiently high to be detected.
T = 350 MeV
T = 300 MeV
T = 250 MeV
∆ystop ~ 2 – 3.5

10. Stable Strangelet interaction in CASTOR MC-algorithm
Strangelet is considered with radius:
Mean interaction path:
Strangelets passing through the detector collide with W nuclei:
Spectator part is continuing its passage.
Wounded part produces particles in a standard way.
Particles produced in successive interactions initiate electromagnetic-nuclear cascades.
Process ends when strangelet is destroyed.
E. Farhi, R. Jaffe, Phys.Rev.D30(1984)2379; M. Berger, R. Jaffe, Phys.Rev.C 35(1987)213, G.Wilky, Z.Wlodarczyk, J.Phys.G22(1996)L105; E. Gładysz, Z. Włodarczyk, J.Phys.G23(1997)2057
The rescaled r0 is determined by the number density of the
strange matter: n = A/V = (1/3)(nu+nd+ns)
where ni=- ∂Ωi/∂μi; Ω(mi,μi,αs), taking into account the QCD O(αs) corrections to the properties of SQM. s s s

11. Unstable Strangelet in Pb chamber MC Simulation
7 Neutrons

12. Comparison Data with Simulation
Similarity between the experimental data (squares) and simulated cascades produced by a bundle of seven neutrons (full histogram).
Distribution of mutual distance between the consecutive maxima;
Distribution of ratios of the energy contained in the particular maxima to the average energy of the humps.

13. MC - Stable Strangelet in CASTOR
HIJING
CASTOR Geometry configuration
1 layer: 5mm W+2mm quartz plate ~2.4 X0
1 RU = 7 layers per readout unit
16 (in  x 18 (in z) readout channels
Total depth: ~ 10.5 Λint
Low Energy Strangelets (~5 TeV)
may be seen above background.
Depth
HIJING
Depth

14. Stable Strangelet in CASTOR
A=15, E=7.5 TeV
60 pions, 1TeV each
A=10, E=5 TeV

15. Full CASTOR Calorimeter
Segmentation: 14(depth) x 16(azimuth) = 224 channels
Stage II
Stage I

16. HIJING Pb+Pb Event at √s = 5.5 TeVη
GeV
Etot ~ 130 TeV ~ 8 TeV/sector
N < 100/sector
230906
CMS-HI/ Apostolos D. Panagiotou η
GeV

17. Fluctuations in Cascade Profile in Sectors Calorimeter Depth (RUs)
HIJING
Energy
230906
CMS-HI/ Apostolos D. Panagiotou
Calorimeter Depth (RUs)

18. Fluctuations in Energy Distribution in Sectors
HIJING 1 2
En. Distribution in sector / Average En. Distribution 15 16
230906
CMS-HI/ Apostolos D. Panagiotou

19. Strangelet identification & Analysis
Event-by-event analysis
Analysis procedure in 2 steps:
Strangelet signatures
Azimuthal asymmetry
in energy deposition
FluctuationsLongitudinal
transition curves
σsd = standard deviation of the distribution of the energies Ei
<E> = mean energy in sectors
(i = 1 – 16 sectors)
energy distribution per RU
average distribution
Large magnitude of energy
fluctuations in RUs manifest
abnormal transition curves

20. Analysis of HIJING Event
Need to analyze 104 events

21. Energy distributions in CASTOR
HIJING
Strangelet in one sector
Total Energy in Sectors
Energy in RUs
Total Energy in Sectors
Energy in RUs
Average of 16 Sectors
A = E = 7.5 TeV
<E>
Energy
(Depth) RU
Sector
(Depth) RU
Sector

22. Pb+Pb HIJING + Strangelet

23. Pb+Pb HIJING + Strangelet Cascade Profile in Sector
Depth

24. Analysis with Strangelet
Estr = 10 TeV
Estr = 7.5 TeV σE
sector containing
Strangelet + HIJING
sectors containing
HIJING Pb+Pb
EM-cut
only H-section
σfluctuations
EM+H section
230906
CMS-HI/ Apostolos D. Panagiotou

25. Strangelet in between two Sectors Energy Distribution in Sectors
Estr = 7.5 TeV
Sectors with Strangelet
~ 14% with Ei/Ej = 50/50 – 75/25

26. Strangelet in between two Sectors Transition Curves
Estr = 7.5 TeV
HIJING + Strangelet
<HIJING>
<HIJING>
Depth
Depth

27. Analysis with Strangelet in two Sectors
Sectors with Strangelet
EM-cut

28. Strangelets of various Energies
7.5 TeV
10 TeV
Strangelets of various Energies
15 TeV
EM-cut

29. CMS-HI/ Apostolos D. Panagiotou
Comparison of Observed and Input MC Strangelet Efficiency of Identification
Observed Strangelet ≡ Average Energy distribution of mixed event – Energy distribution in sector containing Strangelet
Eobs ~ 97%
230906
CMS-HI/ Apostolos D. Panagiotou

30. Cross Section Estimation for Strangelets
The probability for a hadron-rich ‘Centauro-type’ event, estimated from statistics of Chacaltaya and Pamir experiments for cosmic ray families with visible energy greater than 100 TeV, is about 3%.
In about 10% of these hadron-rich events, strongly penetrating cascades, clusters, or ”halo” were observed. We assume the total probability for “Long Flying Component” (Strangelet?) production in central nucleus-nucleus collisions to be approximately: 0.03 x 0.1 ~ O(10−3).
At LHC kinematics, the percent of Strangelets falling in CASTOR phase space is ~ 10% of total number of Strangelets produced in central Pb-Pb collisions. This quantity depends on the mass and energy of the Strangelet, as calculated by the “Centauro model” MC code CENGEN.
A rough estimation of the total probability for Strangelet production and detection in CASTOR is:
PCASTOR strangelet ≈ 10−3 × 0.1 ≈ O(10−4)
This number, even if it is uncertain by an order of magnitude down, is a very large number !

31. Summary Characteristics of a “Strangelet event”:
1. Sector(s) with much higher energy than the average.
Strong fluctuations in the longitudinal cascade profile of the sector.
Large Ehad/Eem for the event (Hadron-rich event).

32. Astr = Estr = 5 TeV