introduction to hadron physics (one lecture)

7/29/2019 Introduction to hadron physics (one lecture)

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Introduction to Hadron Physics

ZHENG Chuan

2011.5.5


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Matter in nature

Track of Modern Physics


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Where is mass from

proton

electron

hydrogen

me = 0.511 MeV/c2

mp = 938.3 MeV/c2

mu = 1.5 to 3.3 MeV/c2

md = 3.5 to 6.0 MeV/c2

1/1836

E = mc2 m = E/c2

px ~ & E = pcE ~ c/x = 197 MeVfm / 1 fm

Mass is from localization and field energy!


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Strong force

Strong Electromagnetic Weak Gravitational

20 1 10-7 10-36

Two protons in nuclues


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Nuclear force

Nuclear force: residual q-q interaction!

p

p

0p

p

p

n+/-

n

p

Yukawa firstly predicted the existence of mesons.


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Bubble chamber

K- beam

e-

Liquid

hydrogen

Early tracking detector


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K-

e-

Liquid

hydrogen

Bubble chamber

++

e+


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K-

e-

Liquid

hydrogen

Bubble chamber

++

e+

ee

+ +

+

Meson +decay mode


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Quark modelu

Q=+2/3

d

Q=-1/3

sQ=-1/3

s

Q=+1/3Q=-2/3

u d

Baryon: qqqMeson: qq

J P = 0- J P = (1/2)+

Hadron


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Prediction of-

J P = (3/2)+

Liquid

hydrogen

K-

2e+

e-

-0

-

Baryon - was predicted by quark model.


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Prediction of-

Liquid

hydrogen

K-

2e+

0--

e-+

+

+

+

+

Baryon - was predicted by quark model.

J P = (3/2)+


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Prediction of-

Liquid

hydrogen

K-

2e+

e-

-0

0

0

0 0

2

K p K K

p

+

+ + +

+ + + + Barnes et al. PRL 12(1964)204


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Force carrier

e-

e-

= e2/4 ~ 1/137q

q

Qq

q

q

g

sQCD (QuantumChromodynamics)

s

= gs

2/4 ~ 1

QED (QuantumElectrodynamics)

Charge of QED is electric charge.

Charge of QCD is called Colorwith 3 values

labelled red, greenand blue. -s ss

Gluon carry the charge

of the strong interaction!


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Experimental evidence of quarksand gluons


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Deep inelastic scattering

e-

Elastic scattering on spin 0

q2 = (k-k)2

Inelastic scattering on spin 1/2

Q2 >> 1 GeV2

22

Mott

2 3

d dF(q )

d d

F(q ) ( ) di q rr e r

=

=

i

i

2 2

22 1'

Mott

2' 2

1,2

F (Q , ) F(Q , )d d 2tand dE d 2 M

QE-E, x F (Q ,x)

2M

= +

= =

i i

Structure functions


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Deep inelastic scattering

Nucleon is composed ofspin pointlike particles!

2 2

2 1

2 2

2

F (Q , x ) 2 x F (Q , x )

F (Q , x ) G (Q ) xf(x)

=

=

x: the fraction of the entireproton momentum carried

by the parton in nucleon

When x is fixed, F2 is thedipole form factor.


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Quarks in e+e- annihilation

R =

e+

e-

+-

e+

e-

qq

2 2 2 2 23

2 1 1 23 [( ) ( ) ( ) ( ) ...]

3 3 3 3i

i

Q= = + + + +

color u d s c

ss

cc

uu

bb

dd

211/310/3


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Quarks in e+e- annihilation

R =

e+

e-

+-

e+

e-

qq

2 2 2 2 23

2 1 1 23 [( ) ( ) ( ) ( ) ...]

3 3 3 3i

i

Q= = + + + +

color u d s c

ss

cc

uu

bb

dd

211/310/3

Proving the flavor and color properties of quarks!


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Experimental evidence of gluons

Observation of 3-jets event in e+

e-

annihilation isthe direct experimental evidence of gluons!


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QCD Theory of strong interaction


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QCD Asymptotic freedom

0.8 fmEMV( )rr

= 4V( )3

sr k rr

= +

k ~ 1 GeV/fm

+ - q q

Asymptotic freedom is the most important featureof QCD!


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QCD Asymptotic freedom

r ~ 1/Q small r

Strong coupling becomes less at smaller distance!


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QCD Quark confinement

meson

baryon

All hadron states and physical observablesare color-singlets!


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Chiral symmetry breaking

Left Right

u u

d d

22

( ) ( ) 10 MeVu d u dM

m m m m mf

= + +

( )

QCD gluon quark

quark

quark, ,

f fff

f u d u d

L L L

L q i D m q

L ui D u di D d m uu m dd

=

= +

= +

= + + +

Chiral symmetry

Quark mass

breakingmu

= md

= 0

Chiral symmetry is an approximate symmetryof strong interaction!

St d d d l


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Standard model


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Frontiers of hadron physics

Multiquark components

Quark Gluon Plasma

Exotic states


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Hadron spectrum mesons

Very similar to electron configuration

JPC = 0-+, 0++, 1--, 1+-,

1++, 2++

JPC = 0--, 0+-, 1-+, 2+-

Allowed combinations

Not allowed: exotic

H d t l b ll


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Hadron spectrum glueball

f0(980)

f0(1370)f0(1500)f0(1710)

Lattice QCD

Glueball

spectrum

q q

q q

g

g

g g Glueball is allowed in QCD!

Amsler Phys. Reports 389(2004)61

Hadron spectr m bar ons


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Hadron spectrum - baryons

Baryon spectrum isless understood!


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Hadron spectrum - multiquarks

Proton: |p> ~ |uud> +

1|[ud][ud]d> + 2|[ud][us]s> +

+KN

Nucleon has multiquark components?

PRL 91 (2003) 012002

2003-2004: 11 big accelerator labsreported Pentaquark findings, but 8other labs found no evidence of it.

The Pentaquark is not in goodhealth, but it is still alive!

Zou and Riska PRL 95 (2005) 072001


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Internal structure of proton

Nucleon has multiquark components!

x

xf(x)

Phases of quark matter


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Phases of quark matter

(Net Baryon Density)

Relativistic heavy

ions collision:

Au+Au Pb+Pb at 100 GeV/nucleon

(RHIC-STAR 2001)

at 1380 GeV/nucleon

(LHC-ALICE 2010)

To know the early universe after the Big Bang!


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Particle detector


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Principle of particle detecting

Tracking chamber (1)


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COSY-WASAMDC



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0

2

4

6

8

10

12

14

E

MWPC

Drift

volume Charged

particl

etrack

Drifting electrons

from primary ionization

Drift field

Gating grid

Anode & Field wires

Cathode

Cathode

-HV

RHIC-STAR

TPC


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Electromagnetic calorimeter (1)

CsI crystalX0 = 1.86 cm

L = 30 cm ; R = 5 cm

Yellow: Red: e+

Green: e-


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Electromagnetic calorimeter (2)

beam

SLAC-Babar COSY-WASA

d i l i ( )


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Hadronic calorimeter (1)

H d i l i (2)


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Hadronic calorimeter (2)

IMP - Neutron Wall

P ti l id tifi ti


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Particle identification

For long-lived charged particles!

2 2 22 2max

2 22 TdE 1 ln

dx 2 I

emcz

0P m c=


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Invariant mass

Example:

0 ,

For short-lived resonant particles!

Minv2 = (E1 + E2)

2 (p1 +p2)2

Mi i


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Missing mass

For the missed particles in the detection!

Example: pd3He X

MX2 = (Ep + md - EHe)

2 (pp - pHe)2

beam target beam

(782)


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Experimental facility

Accelerator


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Accelerator

CERNSynchrotrons

SLAC (Standford

Linear ACcelerator)

Linear and Ring shape!

COoler SYnchrotron (J uelich)


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COoler SYnchrotron (J uelich)

COSY in ~1993

COSY (Cooler Synchrotron)

Circumference 184 m

Beam

(polarized and unpol.)

Proton

/deuteron

Luminosity

(cluster, pellet target)

~1031 cm-2s-1

Beam lifetime a few minutes

to an hour

Beam momentum 0.3 3.7

GeV/c

Intensity (particles) 1010 - 1011

Preparation time a few seconds

HIRFL CSR (Lanzhou)


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CSRm:1.1 AGeV(12C6+)

CSRe:0.76 AGeV (12C6+)

SFC:up to 10 AMeV

SSC:up to 100 AMeV

CSRm:up to 2.8 GeV

proton beam forHadron Physics

HIRFL-CSR (Lanzhou)

HIRFL CSR (Lanzhou)


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HIRFL-CSR (Lanzhou)CSRe

CSRm

Giant detectors at LHC


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Giant detectors at LHC

WASA (J uelich)


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WASA (J uelich)

Detector has the similar layer structure,no matter its big or small!

WASA (J uelich)


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WASA (J uelich)

Superconducting solenoid

HPLUS (Lanzhou)


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HPLUS (Lanzhou)

beam

p/d frozen-pellet target

Detector simulation


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Detector simulation

DAQ and Data


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WASADAQ system

Total channels: 3630; Data rate: 3~4 TB/day!

Summary


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Summary

Quarks and gluons are in reality.

Quantum ChromoDynamics is the basictheory of the strong interaction.

Hadron spectrum, the internal structure of

nucleon and the phases of QCD are thefrontiers of hadron physics.

Particle detectors are the experimentaltools which have similar layer structure.

Big experiment needs big collaboration.

introduction to hadron physics (one lecture)

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