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![Page 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 .](https://reader035.fdocuments.in/reader035/viewer/2022062303/551c4c1c550346b1458b4ac6/html5/thumbnails/1.jpg)
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
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● Motivation: Unconventional Events in Cosmic Rays
● Phenomenological Models & MC Simulations
● “Strangelet” Identification Analysis● Summary
Outline
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Homogeneous thick lead chamber
Centauro
Hadron – Rich CR Events
Normal
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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
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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-
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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
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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
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MC Radial Acceptance of CASTOR
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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
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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
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Unstable Strangelet in Pb chamber
MC Simulation
7 Neutrons
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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
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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
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A=15, E=7.5 TeV
A=10, E=5 TeV 60 pions, 1TeV each
Stable Strangelet in CASTOR
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Full CASTOR Calorimeter
Stage I
Stage II
Segmentation: 14(depth) x 16(azimuth) = 224 channels
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230906 CMS-HI/ Apostolos D. Panagiotou
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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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230906 CMS-HI/ Apostolos D. Panagiotou
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Fluctuations in Cascade Profile in Sectors
Calorimeter Depth (RUs)
En
ergy
HIJING
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230906 CMS-HI/ Apostolos D. Panagiotou
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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
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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
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Analysis of HIJING Event
Need to analyze 104 events
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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>
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Pb+Pb HIJING + Strangelet
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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
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Estr = 7.5 TeV
Strangelet in between two Sectors Energy Distribution in Sectors
Sectors with Strangelet
~ 14% with Ei/Ej = 50/50 – 75/25
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Estr = 7.5 TeV
<HIJING><HIJING>
Strangelet in between two Sectors Transition Curves
Depth Depth
HIJING + Strangelet
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Analysis with Strangelet in two Sectors
EM-cut
Sectors with Strangelet
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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
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• 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
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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
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Astr = 15 Estr = 5 TeV