Badanie przejscia fazowego i poszukiwanie

Transkrypt

Badanie przejścia fazowego i poszukiwanie punktu krytycznego
w eksperymencie NA61/SHINE przy SPS CERN
Magdalena Kuich
Uniwersytet Warszawski, Wydział Fizyki
Sympozjum doktoranckie
Warszawa – Fizyka – Kraków
4 III 2016, Kraków
Magdalena Kuich (Uniwersytet Warszawski)
Badanie przejścia fazowego i poszukiwanie . . .
Warszawa–Fizyka–Kraków 2016
1 / 14
Contents
1
Motivation
2
Investigation strategy
3
Onset of deconfinement
Analysis methods
Results
QGP signatures
4
Critical point
Analysis methods
Results
5
Summary
2 / 14
How to understand phases of interacting matter
electromagnetic interactions
strong interactions
3 / 14
Our thermometer – NA61/SHINE detector
~13 m
A large acceptance
hadron spectrometer
MTPC-L
ToF-L
Vertex magnets
VTPC-1
Target
GAP
TPC
ToF-F
VTPC-2
Beam
PSD
S4
x
CEDAR
S1
THC
V0
S2
S5
p
V1
ToF-R
V1
MTPC-R
y
BPD-1
BPD-2
BPD-3
z
Beam particles measured
in set of counters and
detectors
Charged tracks measured
in set of 5 TPCs →
measurement of q, p and
identification via dE /dx
3 ToF walls:
identification via time of
flight measurement
(Be+Be collision at 75A GeV/c measured in the NA61/SHINE detector)
Projectile Spectator
Detector counts the
non-interacting nucleons
of the beam nuclei
JINST 9 P06005
4 / 14
The way to search – the strong interaction programme of NA61/SHINE
T (MeV)
Two-dimensional scan in collision energy and the system size translates into scan of
the phase diagram of strongly interacting matter (CERN-SPSC-2006-034):
⇒
Freeze-out parameters
200
150A GeV/c
180
160
13A GeV/c
NA61 collected data
p+p
C+C
Si+Si
Pb+Pb
p+p
140
NA49
100
Be+Be
Ar+Sc
Xe+La
Pb+Pb
NA61 future data
120
200
300
400
500
600
µ (MeV)
B
The scan allows to study the onset of deconfinement and search for the critical
point of the phase transition
- the onset of deconfinement via measurements of particle multiplicities
- the critical point via study of fluctuations
PRC73:044905
shine.web.cern.ch
5 / 14
Onset of deconfinement
6 / 14
Analysis methods
h− analysis method estimates number of π − in large phase space
Measurement of the average energy loss (hdE /dx i) in the TPCs allows to
separate particles of various masses which combined with measurements of
particle time of flight (tof ) in the ToF detectors provides excellent separation of
different hadron species close to the mid-rapidity region. Thanks to these
methods we can identify particles.
dE/dx [arb. units]
0.8
0.9
1
1.1
1.2
1.3
900
Mean
0.1257
0.3068
measureRMS
points
fitted function
700
Entries
18224
Mean
1.116
RMS
0.06219
600
fitted pions
500
fitted kaons
400
fitted protons
1.4
px
800
300
200
hist_0_9_4_0
Entries
Mean
K
-
RMS
14509
1.262
0.07598
0.1257
0.3068
1.5
p
K
CC_1
p
π
0.8
1
1.2
1.4
0
200
400
600
800
1000
e
10
1200
−0.5
1400
0
102
RMS
π-
Mean
< 0.4 [GeV/c]
18224
T
py
0.3 < p
103
0
1
Tot
Entries
negative particles
7.94 < p
< 10.00 [GeV/c]
0.5
counts
mass2 [GeV2/c4]
100
104
1.6
1.8
dE/dx [a.u.]
7 / 14
Results
1.4
EPJC74:2794
1.2
1
5 NA61/SHINE
preliminary
1
0.8
0.6
0.6
0.4
0.4
0.2
0.2
1
0
0
-4
2
3
4
y
3
-3
-2
-1
0
1
2
3
+pz
y = 21 ln EE −p
z
4
y
example of spectra
obtained with dE /dx and
tof − dE /dx analysis
methods in p+p 80
GeV/c and K+ pT spectra
for various energies
identification of 6 kinds of
particles but in smaller
phase space
one kind of particles but
broad phase space
2
K+ in p+p 80 GeV/c
1
0.8
T
1
spectra of π − obtained
with h− analysis method
in p+p and Be+Be
interaction
4
0.8
0
0
150A GeV/c
Be+Be; 0 - 5%
Be+Be; 5 - 10%
Be+Be; 10 - 15%
Be+Be; 15 - 20%
158A GeV/c
p+p
6
0.6
0.4
N
pr A61
el /S
im H
in IN
ar E
y
0.12
0.1
0.08
+
p+p → K + X
1
0.0 < y < 0.2
10-1
158 GeV/c × 8
0.06
0.04
0.2
0
−1
K+ pT spectra
0.14
T
158 GeV/c
1.2
d2n [1/(GeV/c)]
dydp
1.4
dn
dy
π − in Be+Be
7
p [GeV/c]
T
p [GeV/c]
π − in p+p
80 GeV/c × 6
10-2
0
1
2
3
y
0
NA61/SHINE
preliminary
40 GeV/c × 4
30.9 GeV/c × 2
0.02
20 GeV/c × 1
10-30
0.2
0.4
0.6
0.8
1
1.2
p GeV/c
T
8 / 14
NA61/SHINE
preliminary
T [MeV]
K +/π+ (y≈0)
QGP signatures
K+
400
y≈0
NA61/SHINE
preliminary
0.2
200
0.1
p+p Pb+Pb Au+Au
p+p Pb+Pb Au+Au
SPS(NA61 p+p)
WORLD(p+p, 4π)
AGS
SPS(NA49)
0
SPS(NA61 p+p)
WORLD(p+p)
AGS
SPS(NA49)
RHIC
LHC(ALICE)
1
102
104
sNN [GeV]
In central Pb+Pb collisions a sharp peak in
SPS energy range...
RHIC
LHC(ALICE)
102
1
K+
π+
104
sNN [GeV]
ratio at mid-rapidity is visible in
Energy dependence of the inverse slope parameter T of kaon spectra exhibits
rapid changes in the SPS energy range...
...what is interpreted as due to the onset of deconfinement.
Shadows of these structures seem to be visible also in p+p interactions.
Be+Be and Ar+Sc data soon.
PRC69:044903, PRC79:034909(STAR); PLB736(ALICE), EPJC71:1655(ALICE)
ZPC65(π), ZPC71(K), PRC72:014908(BRAHMS); EPJC71:1655(ALICE), PRL109:252301(ALICE)
9 / 14
Critical point
10 / 14
pT and multiplicity fluctuations of non-identified particles
⇒
Σ – strongly intensive measure used to study fluctuations (in GCE does not depend on
its volume)
PT – sum of particle transverse momenta in a given event
N – particle multiplicity in a given event
Σ [PT , N] =
1
hNiω [PT ] + hPT iω [N] − 2 (hPT Ni − hPT ihNi)
ω [pT ] hNi
h
i
where:
ω [PT ] =
hPT2 i − hPT i2
hPT i
ω [N] =
hN 2 i − hNi2
hNi
ω [pT ] =
pT2 − pT 2
pT
11 / 14
Summary of search for the critical point using pT and N fluctuations in
NA61/SHINE: p+p and Be+Be interactions
No centrality dependence in Be+Be
No sign of any anomaly that can be attributed to CP (both in p+p and Be+Be)
... waiting for Ar+Sc results ...
M. Gaździcki, P. Seyboth, arXiv:1506.08141; based on T. Czopowicz, CPOD 2014 (slides and arXiv:1503.01619)
12 / 14
Summary
Eksperyment NA61/SHINE bada materię oddziałującą silnie, w obszarze progu na
produkcję plazmy kwarkowo-gluonowej.
Eksperyment ma potencjał odkrywczy i wykonuje precyzyjne pomiary zderzeń
hadronów:
poszukuje punktu krytycznego materii oddziałującej silnie poprzez badanie
fluktuacji produkowanych hadronów
bada próg na produkcję plazmy kwarkowo-gluonowej przez pomiary widm średniej
krotności cząstek
a także wykonuje referencyjne pomiary widm hadronów dla eksperymentów
neutrinowych (T2K, DUNE, . . . ) i promieni kosmicznych (Pierre Auger, . . . )
Pierwsze wyniki wskazują na brak sygnatur punktu krytycznego w zderzeniach lekkich
jąder. Obserwowane są natomiast niespodziewane struktury w zależnościach
energetycznych widm hadronów produkowanych w oddziaływaniach p+p.
W eksperymencie uczestniczy około 150 fizyków z 30 instytucji na świecie, w tym
7 z Polski.
13 / 14
Moja rola w eksperymencie:
badanie przejścia fazowego w oddziaływaniach Be+Be metodą tof –dE /dx ,
kalibracja prędkości dryfu elektronów w TPC,
modernizacja i rozbudowa systemu pomiaru prędkości dryfu,
obsługa, konserwacja i rozbudowa systemu gazowego komór TPC eksperymentu
NA61.
Dziękuję za uwagę.
14 / 14
Additional slides
15 / 14
3. e
tim
e
lec
tr
is m ic sig
nal
ea
on sured
the
pad
arr
ay
Working principle of a TPC
readout plane
R
electric field (drift)
magnetic field
2. electrons drift towards the readout plane
R
measured
particle
R
R
ises th
cle ion
e gas
ti
ary par
1. prim
field cage plate
Voltage
R divider
for the
field cage
R
R
HV
Charged particle detaches electrons from the atoms of the gas (ionisation)
The electrons drift in homogeneous electric field towards the readout plane
Registered signal time and pad position allow for 3D track reconstruction
Magnetic field (if any) is parallel to the electric field, so it doesn’t affect the drift
16 / 14
Charge collection – gas amplification on sense wires
At the end of drift the electrons reach
thin (φ ∼ 20µm) sense wires near the
readout plane.
The electric field is very high close to a thin wire: E(r) ∼ HV/r
Electrons accelerate in the electric field and ionise atoms of the gas. The process
repeats creating an avalanche of electrons.
As the electrons get collected on the wire, they generate an electromagnetic pulse
on the read-out pads, high enough to be registered by the electronics.
The gas amplification effect is used in many other detector types: (multi-)wire
chambers, Geiger counters, resistive plate chambers, GEM. . .
17 / 14

Badanie przejscia fazowego i poszukiwanie

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