Searching for Strange Quark Matterwith the CMS/CASTOR Detector at the
LHC
P. Katsas, A.D. Panagiotou, E. Gladysz
for the CMS/CASTOR Group
http://cmsdoc.cern.ch/castor/
CMS-HI meeting, 23-9 2006
● Motivation: Unconventional Events in Cosmic Rays
● Phenomenological Models & MC Simulations
● “Strangelet” Identification Analysis● Summary
Outline
Homogeneous thick lead chamber
Centauro
Hadron – Rich CR Events
Normal
Measurement settings:
100 μm shower core diameter threshold ~ 3 TeV
(Strangelet ?)
3.6 λI
3.2 λI
3.6 λI
1.5 λI Hadron limit
Hadron limit
CENTAURO FIREBALL EVOLUTION
56A + 14N
u, d g s s
QUARK MATTER FIREBALL
in the baryon-rich fragmentation region
High q suppresses production
of (u u) , (d d), favoring g s s
K+, K0 carry out:
strangeness, positive charge, entropy
CENTRAL COLLISION
at the top of the atmosphere
Ep ~ 1740 TeV
u, d,s
K+
K 0
(u s)
(d s)
u
s
d
(pre-equilibrium) KAON EMISSION
SQM FIREBALL
EXPLOSION
StrangeletHG
...
HG
B¼ < 190 MeV B¼ > 190 MeV
Stabilizing effects of s quarkslong lived state
~75 non strangebaryons + strangelet
(A ~ 10 -15)
Strangenessdistillationmechanism
C. Greineret al., Phys. Rev. D38
(1988)2797
Estimates for Centauro at LHC
• Energy density ε ~ 3 - 25 GeV/fm 3, • Temperature T ~ 130 - 300 MeV• Baryochemical potential µb ~ 0.9 - 1.8 GeV/fm3
CNGEN Centauro & Strangelet
Generator
Phys. Rev. D45(1992)3134 Astroparticle Phys. 2(1994)167 Astroparticle Phys. 13(2000)173
Phys. Atom. Nucl. 67(2004)396
anti-
N = 2352N = 108
Multiplicity in CASTOR Acceptance
CENTAURO HIJING
Low multiplicity High multiplicity mostly baryons + kaons dominated by pions
Simulations - CNGEN
5.2 < < 6.5
T = 250 MeV, q= 600MeV, ystop = 3.0 idpartidpart
CASTOR
Probability of Centauro & Strangelet Detection
CASTOR
~ 60 % of Centauro decay products and ~ 10% of Strangelets within CASTOR acceptance
= 9 GeV/fm3, T = 250 MeV, q= 330 MeV, ystop = 3.0
Estr (GeV)
5.2< < 6.5
MC Radial Acceptance of CASTOR
Strangelets from Centauro Decay
∆ystop ~ 2 – 3.5
5.2 <
Expected at LHC:● Energy densities up to
є ~ 25 GeV/fm3
● ∆ystop ~ 2 - 3.5
HIJING,VENUS
● ∆ystop ~ 2.3
BRAHMS-RHIC
several to ~ 25% strangelets with energies E > 7 TeV, sufficiently high to be detected.
T = 350 MeVT = 300 MeVT = 250 MeV
Stable Strangelet interaction in CASTORMC-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
31
23223s
str31
0
mμμπ
2a12
A3πArR
231
str03
1
W
NWWstr
ArA1.12π
mAλ
nstrstr NAA'
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.
ss s
Unstable Strangelet in Pb chamber
MC Simulation
7 Neutrons
Similarity between the experimental data (squares) and simulated cascades produced by a bundle of seven neutrons (full histogram).
(a) Distribution of mutual distance between the consecutive maxima; (b) Distribution of ratios of the energy contained in the particular maxima
to the average energy of the humps.
Comparison Data with Simulation
MC - Stable Strangelet in CASTOR
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 int
Low Energy Strangelets (~5 TeV)
may be seen above background.HIJING
HIJING
Depth
Depth
A=15, E=7.5 TeV
A=10, E=5 TeV 60 pions, 1TeV each
Stable Strangelet in CASTOR
Full CASTOR Calorimeter
Stage I
Stage II
Segmentation: 14(depth) x 16(azimuth) = 224 channels
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HIJING Pb+Pb Event at √s = 5.5 TeV
Etot ~ 130 TeV ~ 8 TeV/sector N < 100/sector
GeV
GeVη
η
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Fluctuations in Cascade Profile in Sectors
Calorimeter Depth (RUs)
En
ergy
HIJING
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Fluctuations in Energy Distribution in SectorsE
n. D
istr
ibu
tion
in s
ecto
r / A
vera
ge E
n. D
istr
ibut
ion
1
16
HIJING
2
15
Strangelet signatures
Azimuthal asymmetryin energy deposition
FluctuationsLongitudinaltransition curves
sd
iE
EE
Event-by-event analysis Analysis procedure in 2 steps:
average distribution energy distribution per RU
Large magnitude of energyfluctuations in RUs manifestabnormal transition curves
nsfluctuatio
Strangelet identification & Analysis
(i = 1 – 16 sectors)
<E> = mean energy in sectors
nsfluctuatio
σsd = standard deviation of the distribution of the energies Ei
Analysis of HIJING Event
Need to analyze 104 events
HIJING Strangelet in one sector
Energy in RUs Energy in RUs
Energy distributions in CASTOR
(Depth) (Depth)
A = 15 E = 7.5 TeV
Average of 16 Sectors
En
ergy
RU RUSector Sector
Total Energy in Sectors Total Energy in Sectors
<E>
Pb+Pb HIJING + Strangelet
Pb+Pb HIJING + Strangelet Cascade Profile in Sector
Depth
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Analysis with Strangelet
Estr = 7.5 TeV Estr = 10 TeV
EM-cutonly H-sectionEM+H section
sector containingStrangelet + HIJING sectors containing
HIJING Pb+Pb
σE
σfluctuations
Estr = 7.5 TeV
Strangelet in between two Sectors Energy Distribution in Sectors
Sectors with Strangelet
~ 14% with Ei/Ej = 50/50 – 75/25
Estr = 7.5 TeV
<HIJING><HIJING>
Strangelet in between two Sectors Transition Curves
Depth Depth
HIJING + Strangelet
Analysis with Strangelet in two Sectors
EM-cut
Sectors with Strangelet
Strangelets of various Energies
15 TeV
10 TeV
7.5 TeV
EM-cut
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Comparison of Observed and Input MC Strangelet Efficiency of Identification
Eobs ~ 97%
Observed Strangelet ≡ Average Energy distribution of mixed event – Energy distribution in sector containing Strangelet
• 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 !
Cross Section Estimation for Strangelets
Characteristics of a “Strangelet event”:
1. Sector(s) with much higher energy than the average.
2. Strong fluctuations in the longitudinal cascade profile of the sector.
3. Large Ehad/Eem for the event (Hadron-rich event).
Summary
Astr = 15 Estr = 5 TeV