[PPT] - O n s t ra n g e n e s s i n N A 6 1 / S H I N E M a c i e j L e w PowerPoint Presentation

SLIDE 1

E x c i t e d Q C D Kopaonik, Mar142018

O n s t ra n g e n e s s i n N A 6 1 / S H I N E

M a c i e j L e w i c k i

mlewicki@ift.uni.wroc.pl

University of Wrocław

Institute of Theoretical Physics

SLIDE 2

NA61/SHINE’s strong interaction programme

Two-dimensional scan in collision energy and system size probes the phase diagram of strongly interacting matter: Search for the critical point. Study of the

nset of deconfinement.

System size p+p p+Pb Be+Be Ar+Sc Xe+La Pb+Pb 2009/10/11 2012/14/16/17 2011/12/13 2015 2017 2016/18 13 20 30 40 75 150 Beam momentum [A GeV/c]

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 1 / 31

SLIDE 3

NA61/SHINE and the QCD phase-space

Becattini, Manninen, Gaździcki Phys. Rev. C 73, 044905 (2006)

NA61/SHINE NA61/SHINE

T µB √sNN A Unique 2-dimensional scan

f QCD phase-space:

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 2 / 31

SLIDE 4

Section 2 Strangeness and Phase Transition

SLIDE 5

Strangeness and phase transition

confined matter quark-gluon plasma K mesons (anti-)strange quarks gK = 4 gs = 12 2M ≈ 2 · 500 MeV 2m ≈ 2 · 100 MeV

TC ≈ 150 MeV

− →

Phase transition

Lightest strangeness carriers: relatively heavy kaons (M > TC) in the confined phase, relatively light strange quarks (m TC) in QGP.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 3 / 31

SLIDE 6

Strangeness in Statistical Model of Early Stage

toy model

n = gV (2π)3

d3p

1 eE/T ± 1 ≈ gV MT

2π

3/2 e−M/T ≈ gV 2π2

4·45T3

for heavy particles for light particles K π ∝ M T3/2 T3 · e−M/T

T <Nss>/

non-strange

<

>

s u + d + g ∝ T3 T3 = const(T)

Gaździcki, Gorenstein, Acta Phys.Polon. B30 (1999) 2705

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 4 / 31

SLIDE 7

Strangeness in Statistical Model of Early Stage

Temperature dependence

n collision energy in SMES:

sNN [GeV]

5 10 15 20 25 100 150 200 250 300

T[MeV]

Strange/non-strange particle ratio:

sNN

QGP <Nss>/

non-strange

<

>

Crossing the phase transition leads to a decrease of the strange/non-strange particle ratio – the horn-like structure – Mareks’ horn.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 5 / 31

SLIDE 8

Dynamical Approach by Rafelski-Müller

strangeness production in confined matter π + N → K + Y π + Y → Ξ + K π + Ξ → Ω + K π + N → K + Y π + Y → Ξ + K π + Ξ → Ω + K strangeness production in QGP

Rafelski, Müller; Phys. Rev. Lett. 48 (1982) 1066 Koch, Müller, Rafelski; Phys. Rep. 142 (4) (1982) 167

gg → s¯ s τ ≈ 2 × 10−23s. q¯ q → s¯ s ≈ 10× slower. QGP lifetime 2 × 10−23s

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 6 / 31

SLIDE 9

Rafelski-Müller Dynamical Approach

Equilibrium value reached in QGP ← fast strangeness production.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 7 / 31

SLIDE 10

Rafelski-Müller Dynamical Approach

QGP <Nss>/

non-strange

<

>

sNN

Equilibrium value reached in QGP ← fast strangeness production. No enhancement in the confined phase ← slow strangeness production in whole hadronic region.

Glendenning, Rafelski; Phys. Rev. C 31 (3) (1982) 823 Kuznetsova, Rafelski; Eur. Phys. J. C 51 (2007) 113

strangeness / entropy

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 7 / 31

SLIDE 11

Section 3 Strangeness in Heavy Ion Collisions

SLIDE 12

Strangeness in HIC

Most strangeness produced in the form of: The lightest (anti-)strange mesons (M ≈ 0.5 GeV):

◮ K+ – (u¯

s)

◮ K− – (¯

us)

◮ K0 – (d¯

s)

◮

¯ K0 – (¯ ds)

The lightest (anti-)strange baryons (M ≈ 1.1 GeV):

◮ Λ – (uds) ◮ ¯

Λ – (¯ u¯ d¯ s)

Strangeness neutral mesons: (M ≈ 1.0 GeV):

◮ φ – (s¯

s)

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 8 / 31

SLIDE 13

Main strangeness carriers

in A+A collisions at high baryon density

¯ s

strangeness conservation

=

s K+

isospin symmetry

≈

K0

≪

high baryon density

¯ Λ

≪

high baryon density

K−

isospin symmetry

≈

¯ K0

≈

Λ

– sensitive to strangeness content only – sensitive to strangeness content and baryon density

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 9 / 31

SLIDE 14

Strange definitions & approximations

Wanted: experimental measure of strangeness/ entropy Strangeness production: Ns¯

s – number of s-¯

s pairs produced in a collision. 2 · Ns¯

s = Λ + ¯

Λ + K + ¯ K + φ + . . . 2 · Ns¯

s ≈ Λ + K + ¯

K Entropy production ∝ π The experimental ratio defined as: ES = Λ + K + ¯ K π

≈ 2 · Ns¯

s

π ∝ Ns¯

s

multistrange hyperons

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 10 / 31

SLIDE 15

How to measure produced strangeness

Decades ago...

streamer chambers measured:

◮ charge ◮ momentum

strange hadrons identified by reconstruction of their decays:

◮ Λ ◮ K0

s

K0

s = 1 2K0 + 1 2 ¯

K0 4K0

s = 2K0 + 2 ¯

K0 ≈ K0 + K+ + K− + ¯ K0 Λ + 4K0

s ≈ 2Ns¯ s

Es = Λ + 4K0

s

π

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 11 / 31

SLIDE 16

How to measure produced strangeness

Nowadays: TPCs + ToF measured: strange hadrons identified by mass measurement:

◮ K+ ◮ K−

Ns¯

s ≈ K+ + K0 ≈ 2 · K+,

π ≈ 3 2

π+ + π−
Ns¯

s

π ≈ 2 3 K+ π+ ES ≈ 4 3 K+ π+

◮ momenta ◮ charges ◮ masses Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 12 / 31

SLIDE 17

Section 4 Strangeness at NA61/SHINE

SLIDE 18

NA61/SHINE — facility

T

F-L

T

F-R

PSD T

F-F

MTPC-R MTPC-L VTPC-2 VTPC-1 Vertex magnets T arget GAP TPC Beam S4 S5

S2 S1 BPD-1 BPD-2 BPD-3 V1 V1 V0 THC CEDAR

z x y

p

FTPC-1 VD

FTPC-2/3

Beam detectors: position charge mass time TPCs: electric charge momentum dE/dx ToF: tof PSD: EF – energy of projectile spectators reaction plane

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 13 / 31

SLIDE 19

Particle identification — tof-dE/dx

20 40 60 80 100 120

dE/dx [a.u.]

0.8 1 1.2 1.4 1.6 1.8

]

2

)

2

[(GeV/c

2

m

0.4
0.2

0.2 0.4 0.6 0.8 1 1.2 1.4

+

π

+

p

+

e

Be+Be @40A GeV/c

K

20 40 60 80 100 120

dE/dx [a.u.]

0.8 1 1.2 1.4 1.6 1.8

]

2

)

2

[(GeV/c

2

m

0.4
0.2

0.2 0.4 0.6 0.8 1 1.2 1.4

π

p e

Be+Be @40A GeV/c

K-

Very good separation. Very efficient PID in mid-rapidity region.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 14 / 31

SLIDE 20

Particle identification — dE/dx

Probability PID. Applicable in forward-rapidity region.

0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

500 1000

pions protons kaons deuterons electrons sum

[12.59; 15.85) ∈ p [0.20; 0.30) ∈

T

p charge = 1

dE/dx [a. b.] 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

%

5 − 5

σ / ∆

0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

100 200 300 400

pions protons kaons deuterons electrons sum

[12.59; 15.85) ∈ p [0.20; 0.30) ∈

T

p charge = -1

dE/dx [a. b.] 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

%

5 − 5

σ / ∆

Ar+Sc @30A GeV/c Ar+Sc @30A GeV/c

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 15 / 31

SLIDE 21

Event selection

The PSD is located most downstream on the beam line and measures the projectile spectator energy EF of the non-interacting nucleons of the beam nucleus. The energy measured by the PSD is used to select events classes corresponding to the collision "violence" (≈ centrality).

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 16 / 31

SLIDE 22

Section 5 Results on Strangeness

SLIDE 23

Results on strangeness production

Results from NA61/SHINE on identified hadrons produced in strong and electromagnetic processes in primary interactions: Ar+Sc

[CPOD 2017, arXiv:1712.02417]

Be+Be

[Nucl. Phys. A 967, 35 (2017)]

p+p

[Eur. Phys. J. C74 (2014) 2794, Eur. Phys. J. C77 (2017) 671]

World data on Pb+Pb, Au+Au, C+C, Si+Si and p+p: NA49

[Phys.Rev. C77, 024903 (2008)], [Phys.Rev. C66 (2002) 054902], [Phys.Rev. C86 (2012) 054903] [Eur. Phys. J. C68 (2010) 1], [Eur. Phys. J. C45 (2006) 343]

ALICE

[Phys. Lett. B736 (2014) 196], [Eur. Phys. J. C71 (2011) 1655], [Phys. Rev. Lett. (2012) 109]

STAR [Phys. Rev. C79 (2009) 034909], [Phys. Rev. C96 (2017) 044904] BRAHMS [Phys. Rev. C72 (2005) 014908] p+p world data [Z. Phys. C65 (1995) 215], [Phys. Rev. C69 (2004) 044903]

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 17 / 31

SLIDE 24

mT spectra and inverse slope parameter

[GeV]

+

K

m

T

m 0.0 0.2 0.4 0.6 0.8 1.0 ]

1

)

2

[(GeV/c

T

dydm n

2

d

T

m 1

3

10

2

10

1

10 1 10

2

10

3

10

N A 6 1 / S H I N E p r e l i m i n a r y 75A GeV/c Pb+Pb Be+Be p+p 0) ≈ y (

+

K

[GeV]

+

K

m

T

m 0.0 0.2 0.4 0.6 0.8 1.0 ]

1

)

2

[(GeV/c

T

dydm n

2

d

T

m 1

3

10

2

10

1

10 1 10

2

10

3

10

N A 6 1 / S H I N E p r e l i m i n a r y 75A GeV/c Pb+Pb Be+Be p+p 0) ≈ y (

K

mT spectra at mid-rapidity fitted with an exponential function 1 mT d2n dmTdy = A exp

−mT

T

which well describes K spectra for all beam momenta and all reactions

The energy dependence of the inverse slope parameter T was predicted to be sensitive to the phase transition between confined matter and QGP.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 18 / 31

SLIDE 25

Inverse slope parameter

"step" plot

[GeV]

NN

s 1

2

10

4

10 T [MeV] 200 400

+

K

≈ y

[GeV]

NN

s 1

2

10

4

10 T [MeV] 200 400

K

≈ y

Inverse slope parameter T (vague temperature analogy) – a parameter in fit to transverse mass spectra:

dn mTdmT ∼

= A exp − mT

T

A plateau in the phase transition region (
SNN ≈ 10 GeV) ← predicted by SMES.

Be+Be points slightly above p+p and both significantly lower than heavy ions.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 19 / 31

SLIDE 26

Inverse slope parameter

Extrapolation of Ar+Sc points to T(y ≈ 0) falls close to Pb+Pb, while smaller systems show significantly smaller values.

y 0.5 1 1.5 2

T [MeV]

50 100 150 200 250

GeV/c A 30

y 0.5 1 1.5 2

T [MeV]

50 100 150 200 250

GeV/c A 40

y 0.5 1 1.5 2

T [MeV]

50 100 150 200 250

GeV/c A 75

Ar+Sc

+

K

_

K Pb+Pb

+

K

_

K p+p

+

K

_

K Be+Be

+

K

_

K C+C

+

K

_

K Si+Si

+

K

_

K

NA61/SHINE NA49 Preliminary

Ar+Sc Ar+Sc Ar+Sc

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 20 / 31

SLIDE 27

Energy dependence

"horn" plot [GeV]

NN

s 1

2

10

4

10 0) ≈ (y

+

π /

+

K 0.1 0.2

SPS NA61/SHINE AGS SPS NA49 RHIC

Pb+Pb Au+Au p+p

LHC

Rapid change in strangeness production observed in Pb+Pb – the horn. Plateau-like energy dependence in p+p data.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 21 / 31

SLIDE 28

Collision energy dependence of strangeness production

Rafelski-Müller

QGP <Nss>/

non-strange

<

>

sNN

[GeV]

NN

s 1

2

10

4

10 0) ≈ (y

+

π /

+

K 0.1 0.2

AGS SPS NA49 RHIC

Pb+Pb Au+Au

LHC

SMES

sNN

QGP <Nss>/

non-strange

<

>

Qualitatively, heavy-ion data follows dependence predicted by SMES. The dependence predicted by the Rafelski-Müller model is in contradiction with heavy-ion data.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 22 / 31

SLIDE 29

PHSD model with & without Chiral Symmetry Restoration

in the confined phase

Without CSR – prediction of PHSD qualitatively resembles predictions of the Rafelski-Müller model. With CSR – enhanced strangeness production in the confined phase. The strange quark mass used in the string decay Schwinger-formula in assumed to decrease with energy density, while still in the confined phase. Palmese et al. , PRC94 (2016) 044912

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 23 / 31

SLIDE 30

Summary – Model predictions with transition to QGP

QGP

equilibrium

SMES PHSD RM

<Nss>/

non-strange

<

>

sNN

High energies – all three models with phase transition predict the strange/non-strange particle ratio close to the one for the equilibrium QGP. At low collision energies (in the confined matter):

◮ RM model predicts: a) large equilibration time,

b) insignificant strangeness enhancement wrt. initial state.

◮ PHSD cures this problem reducing the strange quark mass in string decays. ◮ SMES overcomes it by postulating the statistical particle production at early

stage of collisions.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 24 / 31

SLIDE 31

System size dependence of strangeness production

[GeV]

NN

s 1 10

2

10 0.2

〉

+

π 〈 〉

+

K 〈

SPS NA61/SHINE SPS NA61/SHINE WORLD (p+p) AGS SPS NA49 RHIC

Pb+Pb Au+Au p+p Ar+Sc

/

[GeV]

NN

s 1

2

10

4

10 0) ≈ (y

+

π /

+

K 0.1 0.2

SPS NA61/SHINE AGS SPS NA49 RHIC

Pb+Pb Au+Au

LHC

p+p Be+Be

SPS NA61/SHINE

Ar+Sc placed in between light and heavy systems. Be+Be very close to p+p.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 25 / 31

SLIDE 32

System size dependence

<W> 1 10

2

10

3

10 0) ≈ (y

+

π /

+

K 0.1 0.15 0.2 0.25

p+p Be+Be Pb+Pb NA61/SHINE preliminary NA49

c GeV/ A 30

WNM

Be+Be resembles closely the p+p data. Ar+Sc much closer to Pb+Pb

Similar behavior at all energies and in the measurement of fluctuations. → Another threshold of collisions dynamics – onset of fireball.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 26 / 31

SLIDE 33

System size dependence of strangeness production - SMES

<W> 1 10

2

10

3

10 0) ≈ (y

+

π /

+

K 0.1 0.15 0.2 0.25

p+p Be+Be Pb+Pb NA61/SHINE preliminary NA49 c GeV/ A 30 SMES WNM

SMES predicts very different system size dependence of K+/π+ ratio than the one measured by the NA61/SHINE experiment. System size dependence predicted by SMES is due to diminishing effect of the canonical strangeness suppression with increasing volume within statistical models.

Poberezhnyuk, Gaździcki, Gorenstein, Acta Phys.Polon. B46 (2015) 10

p+p Pb+Pb Be+Be

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 27 / 31

SLIDE 34

System size dependence of strangeness production - PHSD

> 1 10

2

10

3

10 0) ≈ (y

+

π /

+

K 0.1 0.15 0.2 0.25

p+p Be+Be Pb+Pb NA61/SHINE preliminary NA49 c GeV/ A 30

<W> 1 10

2

10

3

10 0) ≈ (y

+

π /

+

K 0.1 0.15 0.2 0.25

p+p Be+Be Pb+Pb NA61/SHINE preliminary NA49 c GeV/ A

158

A 150

<W> 1 10

2

10

3

10 0) ≈ (y

+

π /

+

K 0.1 0.15 0.2 0.25

] ] ] ] p+p Be+Be C+C Si+Si Pb+Pb NA61/SHINE preliminary NA49

c GeV/ A

158

A 150 WNM pHSD

PHSD predicts increase of strangeness production with system size at low collision energies (<10 GeV) and decrease at high collision energies (>10 GeV). PHSD predictions in disagreement with data at high energies.

Palmese et al., PRC94 (2016) 044912

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 28 / 31

SLIDE 35

The Two Onsets

Onset of deconfinement: beginning of creation of QGP with increasing collision energy (√sNN). Onset of fireball: beginning of creation of large clusters of strongly interacting mater in A+A collisions with increasing nuclear mass number (A).

A √sNN

(collision energy) (atomic mass)

Pb+Pb Ar+Sc Be+Be p+p ≈ 10 ≈ 10

[GeV]

Onset of fireball Onset of deconfinement

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 29 / 31

SLIDE 36

Summary

1 Models of strangeness production in phase transition were reviewed.

Dynamical and statistical approaches were compared.

2 NA61/SHINE’s results on p+p, Be+Be (preliminary) and Ar+Sc (preliminary) were

presented:

◮ transverse mass mT spectra of kaons and inverse slope parameter T, ◮ mean multiplicities of kaons.

3 Energy dependence of strangeness production in light and heavy systems

was reviewed.

4 Clear qualitative difference between light (p+p, Be+Be) and heavy

(Ar+Sc, Pb+Pb) systems measurements observed.

5 It was found that none of existing models can reproduce measured system

size dependence.

6 Two threshold behaviors (onsets) were observed: the onset of deconfinement

and the onset of fireball.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 30 / 31

SLIDE 37

Thank you for your attention!

SLIDE 38

BACKUP SLIDES

SLIDE 39

The Two Onsets

Percolation approach: Increasing nuclear mass → density of clusters (strings, partons...) increases → Probability of cluster overlapping increases. → Conservation laws act on the whole cluster. This approach does not explain equilibrium properties of large clusters.

Physica A96 (1979) 131-135; Phys. Lett. B97 (1980) 128-130; Nucl. Phys. B390 (1993) 542-558; Phys. Rev. Lett 77 (1996) 3736-3738; Phys. Rev. C72 (2005) 024907

AdS/CFT correspondence: AdS (gravity) - formation of a black hole horizon, the information trapping takes place when critical values of model parameters are reached. CFT (QCD) - only starting from a sufficiently large nuclear mass number the formation of the trapping surface in A+A collisions is possible.

Prog. Part. Nucl. Phys. (2009) 62; Phys. Rev. D79 (2009) 124015

A √sNN

(collision energy) (atomic mass)

Pb+Pb Ar+Sc Be+Be p+p ≈ 10 ≈ 10

[GeV]

Onset of fireball Onset of deconfinement

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 1 / 11

SLIDE 40

Predictions of SMES

step kink horn

Plateu in "temperature" dependence on collision energy. Enhancement of entropy production in QGP phase (per participating nucleon). Suppresion of strangeness production in QGP phase.

[GeV]

NN

s 1

2

10

4

10 T [MeV] 200 400

+

K

≈ y

Experimental results – confirming SMES predictions. Signatures of PT happen all at the same √sNN.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 2 / 11

SLIDE 41

Strangeness suppression in Q-state

gs

W, gs Q – numbers of internal dof of (anti)strangeness carriers in W-, Q-state.

The entropy carried by strange (and antistrange) particles: Ss = gs g S For massless particles of j-th species: Sj = 4Nj, Ns + N¯

s = S

4 gs g And the strangeness to entropy ratio: Ns + N¯

s

S = 1 4 gs g Estimate (for massless dof): Q-state: gs

Q/gQ ≈ 0.22, W-state: gs W/gW ≈ 0.5

Numerical calculations with true masses considered: energy dependent

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 3 / 11

SLIDE 42

Strangeness Enhancement at low energies

At low AGS energies the creation of QGP not expected. Strangeness enhancement cannot be explained on grounds of equilibration times only.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 4 / 11

SLIDE 43

Predictions of Hadron Resonance Gas model

Andronic, Braun-Munzinger, Stachel; Nucl. Phys. A834 (2010) 237C-240C

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 5 / 11

SLIDE 44

Results stand for primary particles produced in strong and electromagnetic processes. Corrections: Results are corrected for:

◮ biases in event selection ◮ reconstruction inefficiency ◮ weak decays ◮ secondary interactions ◮ detector geometrical acceptance.

MC used for corrections: EPOS 1.99 model and GEANT3.2+NA61/SHINE detector simulation. Uncertainties: There are two sources of statistical uncertainties in results:

◮ data uncertainties ◮ MC corrections uncertainties (insignificant).

The systematic uncertainties comes from:

◮ limited precision of simulation and detector description.

For nucleus-nucleus collisions, the event classes are defined by forward energy measured by PSD. Results for p+p collisions refer to all inelastic interactions.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 6 / 11

SLIDE 45

Particle yield extrapolation to full pT acceptance

Examples for Be+Be

[GeV/c]

T

p 0.2 0.4 0.6 0.8 1 ]

1

dy [(GeV/c)

T

n/dp

2

d 0.2 0.4 0.6 0.8 150 GeV/c 75 GeV/c 40 GeV/c 30 GeV/c + X K → Be+Be ≈ y

+

[GeV/c]

T

p 0.2 0.4 0.6 0.8 1 ]

1

dy [(GeV/c)

T

n/dp

2

d 0.2 0.4 0.6 0.8 150 GeV/c 75 GeV/c 40 GeV/c 30 GeV/c + X

K

→ Be+Be ≈ y

In order to obtain the dn/dy yields of K mesons, the data is extrapolated with the exponential function in mT beyond the detector acceptance. dn/(dpTdy) spectra were fitted with the corresponding function in pT. The function integral outside the acceptance region (<10%) is added to the measured yield.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 7 / 11

SLIDE 46

Fitting rapidity distribution

Two symmetrically placed gaussians are used to construct the fitting function: ffit(y) = A σ0 √ 2π exp

−(y − y0)2

2σ2

+

A σ0 √ 2π exp

−(y + y0)2

2σ2

Shape parameters: y0 and σ are fixed to values obtained in NA49’s Pb+Pb.

The amplitude A is the only free parameter. Varying the shape parameters provides an estimate of a systematic error.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 8 / 11

SLIDE 47

Rapidity Distribution

30A GeV/c 40A GeV/c 75A GeV/c

y

2 − 1 − 1 2

dn/dy

1 2 3 4 5 +

K

_

K

y

2 − 1 − 1 2

dn/dy

1 2 3 4 5 +

K

_

K

y

2 − 1 − 1 2

dn/dy

1 2 3 4 5 +

K

_

K

Pb+Pb spectra shape fits Ar+Sc data surprisingly well. Measurements of tof will add data in y ≈ 0 region in the near future.

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 9 / 11

SLIDE 48

dE/dx distribution

Functions are fitted to experimental data by considering the parameters depending on the absorbing material as free fit parameters:

−dE

dx

trunc

= E0 1 β2

K + ln(γ) − β2 − δ(β, XA, a)

E0 contains all the constant factors. K adjusts for the shape of the curve around the minimum. Parameters fitted to the data: E0, K, XA, a

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 10 / 11

SLIDE 49

Truncated mean dE/dxTr distribution

The basic peak shape is assumed to be a sum of asymmetric Gaussians:

dE

dx

total

=

i=d,p,K,π,e

Ni 1

l nl
l

nl √ 2πσi,l exp

− 1

2

x − xi

(1 ± δ) σi,l

2

with widths σi,l (l ≡ npts ≡ # of clusters): σi,l = σ0 √ l

xi

x1

α

(lβ arbitrary fixed at β = − 1

2)

0.00 0.02 0.04 0.06

σil

20 40 60 80 100 120 140 160

npts

0.00 0.05 0.10 0.15 0.20 0.25

σ0 = σil · √ l

Entries 10000 / ndf 2 χ 694.0652 / 126 Constant 3.1985 ± 236.7132 Mean 0.0008 ± 2.3017 Sigma 0.0006 ± 0.0629

Truncated mean <dE/dx> 2.1 2.2 2.3 2.4 2.5 2.6 entries/max 100 200 300 400 500 600 700 800 900

Entries 10000 / ndf 2 χ 694.0652 / 126 Constant 3.1985 ± 236.7132 Mean 0.0008 ± 2.3017 Sigma 0.0006 ± 0.0629

npts=10 npts=20 npts=40 npts=80 npts=160

=694.065

2

χ =0.0628715, σ =2.30172, µ 10: =368.85

2

χ =0.0457802, σ =2.29654, µ 20: =250.676

2

χ =0.0325206, σ =2.29292, µ 40: =155.22

2

χ =0.0234032, σ =2.29092, µ 80: =107.346

2

χ =0.0167061, σ =2.29035, µ 160:

Truncated Mean Distribution

Maciej Lewicki (UWr) Strangeness@NA61/SHINE Kopaonik, Mar142018 11 / 11