Hadron Physics Selected Topics Diego Be(oni INFN, Ferrara, Italy - - PowerPoint PPT Presentation

Hadron Physics Selected Topics

Diego Be(oni INFN, Ferrara, Italy

55th Interna5onal Winter Mee5ng on Nuclear Physics Pre-Conference School Bormio, Italy, 22 Januray 2017

Outline

• Introduction to hadron physics

– The Quark Model – Quantum Chromodynamics – Theoretical Approaches – Experimental Methods

• Selected hot topics

– Heavy Quarkonium – X, Y, Z states – Open Charm – Baryons – Form Factors

• Outlook and conclusions

Hadron Physics 2 Diego Be(oni

Introduction to Hadron Physics

The Quark Model The strong interac5on and QCD Theore5cal approaches Experimental methods

Introduction

Hadron physics is the study of strong interacting hadronic matter in all its manifestations, and the understanding of its properties in terms of the underlying fundamental theory, Quantum Chromodynamics or QCD.

• QCD extremely successful at high energies.
• However it is the long-distance, low-energy regime which governs the

bulk of strong interactions (e.g. it determines the properties of the light-hadron spectrum). It requires understanding of non-perturbative QCD.

• At low energies SU(3)F (flavor) symmetry reasonably successful.

QCD is also an essential ingredient of the Standard Model and it is the incalculable strong matrix element which limit our reach for physics beyond the standard model (e.g. muon (g-2)).

Hadron Physics 4 Diego Be(oni

Quarks

Light quarks mq << ΛQCD q=u, d, s Heavy quarks mQ >> ΛQCD Q=c, b, t mu=1.5 ÷ 4.0 MeV md=4 ÷ 8 MeV ms=80 ÷ 130 MeV “current quark masses” MS at scale 2 GeV mc=1.15 ÷1.35 GeV mb=4.1 ÷ 4.4 GeV mt=174.3±5.1 GeV “running masses” in MS scheme Hadrons containing heavy quarks have masses of order mQ rather than of the order ΛQCD.

Hadron Physics 5 Diego Be(oni

Hadrons in the Quark Model: Mesons

Hadron Physics 6

J = L + S P = (-1)L+1 C = (-1)L+S

Pseudoscalar Mesons Vector Mesons

1S0 3S1 q q

_

Diego Be(oni

Quantum Numbers of Mesons with the Quarks u, d, s 1150 , 1300 ? , 1 1 1400 , 2 1250 ? , 1 1 800 , 1 1 500 , ) ( 1 ) ( ) (

* 1 1 * 2 2 * 2 1

S K D Q A S f f K A H Q B S L K S K S L MeV M I I I J q q S q q L

PC

ε δ φ ω ρ η η π

+ + + + + + − + − − + −

= ʹ = = = ʹ = = = = =

nonet

Hadron Physics 7 Diego Be(oni

Hadrons in the Quark Model: Baryons

Hadron Physics 8

Baryon decuplet Baryon octet

+

= 2 1

P

J

+

= 2 3

P

J

d u u

Diego Be(oni

Hadron Physics 9

Meson States with 4 Flavours

Diego Be(oni

Hadron Physics 10

Baryon States with 4 Flavours

Diego Be(oni

Colour

• Spin-parity
• The wave func5on is symmetric

under exchange of any pair of quarks

• s-wave, parallel spins, the spa5al

and spin wave func5ons are also symmetric.

+

= 2 3

P

J

) ( ) (

6 1 . .

GRB GBR BGR BRG RBG RGB qqq

s c

− + − + − =

colore flavor spin spazio q

ψ ψ ψ ψ ψ =

3

( )

γ β α αβγ α

ψ ψ ψ ε ψ α ψ = =

colore

3 , 2 , 1

The product of the first three factors is symmetric under exchange of any pair of quarks, we require the colour wave func5on to be an5-symmetric All observed hadrons are colour singlets. Colour is confined within hadrons.

Hadron Physics 11 Diego Be(oni

e+e- → hadrons

Hadron production in e+e- annihilation occurs via hadronization of qq pairs produced in the process e+e- → qq. The cross section can be related to the one for e+e- → µ+µ-.

e- e- e+ e+

γ γ

µ- µ+

q q

( )

s e e

2

3 4 α π µ µ σ = →

− + − +

( ) ( )

− + − + − +

→ = → µ µ σ σ e e e q q e e

q 2

3

( ) ( )

∑

− + − + − +

→ = →

q q

e e e adroni e e µ µ σ σ

2

3

color

⎩ ⎨ ⎧ = + = − = t c u q b s d q eq , , , ,

3 2 3 1

Hadron Physics 12 Diego Be(oni

( ) ( )

∑

= → → ≡

− + − + − + q q

e e e adroni e e R

2

3 µ µ σ σ

2 10/3 11/3 5

u+d+s u+d+s+c u+d+s+c+b u+d+s+c+b+t

∑

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + =

q s q

Q e R π α ) ( 1 3

2 2

with QCD corrections

Hadron Physics 13 Diego Be(oni

Quantum ChromoDynamics - QCD

QCD is the theory of quarks, gluons and their interactions. It is part of the standard model. It is a quantum field theory based on the invariance under local gauge transformations in SU(3)c. The QCD lagrangian is: covariant derivative: gluon field tensor:

( )

µν µν µ µ

ψ γ ψ

j j QCD

G G m i 4 1 − − = D L

( )

x ig

j j

∑

=

− ∂ =

8 1 2 j

A D

µ

λ

µ µ

( ) ( ) ( ) ( ) ( )

x x gf x x x G

k j ijk i i i ν µ µ ν ν µ µν

A A A A + ∂ − ∂ =

j ijk j

f

µ

λ A

Gell-Mann Matrices Structure constants Gluons

Hadron Physics 14 Diego Be(oni

Running Coupling Constant

The renormalization of the theory introduces an energy scale: the coupling strength g becomes a “running coupling constant”, i.e. it depends on the energy scale µ. Defining we get: with Nf is the number of quark flavors. The scale parameter Λ is determined empirically: Λ=0.2 GeV for Nf=4.

( ) ( )

π µ µ α 4 /

2

g

s

=

3 / 2 11

f

N − = β

( )

( )

2 2

/ ln 4 Λ = µ β π µ αs

Hadron Physics 15 Diego Be(oni

Hadron Physics 16

Loop Contributions in QCD

Similar to QED same contribu5onfor each flavor (the colour force is flavor independent)

( ) ( )

π µ α π µ α 6 3

2 3 2

→

color factor, for each flavor. New with respect to QED It only gives a numerical factor:

• 8 gluons, larger contribu5on
• opposite sign
• Asympto5c freedom

Diego Be(oni

Hadron Physics 17

Charge screening in QCD and running of αS

QED analogue gluon self coupling in QCD

Diego Be(oni

QCD

Hadron Physics 18

Asymptotic freedom Confinement

Diego Be(oni

( ) ( ) ( )⎟

⎠ ⎞ ⎜ ⎝ ⎛ = x d x u x ψ

( )

ψ γ ψ

5 ,

1 2 1 ± =

L R R a a R R

i ψ τ θ ψ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ → 2 exp

L a a L L

i ψ τ θ ψ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ → 2 exp

( ) ( )L

R

SU SU 2 2 ×

( )

R a R a R

J ψ τ γ ψ

µ µ

2 /

, =

( )

L a L a L

J ψ τ γ ψ

µ µ

2 /

, =

= ∂ = ∂

µ µ µ µ L R

J J

Chiral Simmetry

In the massless quark limit, the QCD Lagrangian della QCD has a global symmetry related to the conserved chirality (handedness) of massless spin ½ particles. With two flavors (Nf=2): These transformations leave LQCD invariant in the m=0 limit: the RH and LH quark components never mix. Six conserved Noether currents: Chiral Symmetry of QCD

Hadron Physics 19 Diego Be(oni

ψ τ γ ψ

µ µ µ µ

2

, , a a L a R a

J J V = + = ψ τ γ γ ψ

µ µ µ µ

2

5 , , a a L a R a

J J A = − =

( ) ( )

∫

+

= x x x d Q

a V a

ψ τ ψ 2

3

( ) ( )

∫

+

= x x x d Q

a A a

ψ τ γ ψ 2

5 3

Vector current: Axial current: The corresponding charges are generators of SU(2) x SU(2): If we consider the strange quark mass small it makes sense to generalize the chiral symmetry to three flavours Nf=3. In this case the three Pauli matrices τa are replaced by the 8 Gell-Mann matrices λa.

Hadron Physics 20 Diego Be(oni

Spontaneous Chiral Symmetry Breaking

There is evidence from hadron spectroscopy that chiral symmetry in the limit m=0 is spontaneously broken. For dynamical reasons the vacuum is symmetric only under the subgroup SU(2)V generated by the vector charge QV. This is the well- known isospin symmetry (for Nf=2) or flavour symmetry (for Nf=3). If the symmetry were not broken we would observe parity doublets and the vector mesons (JP=1-) would be degenerate with the axial mesons (JP=1+), while e.g. M(ρ) = 0.77 GeV and M(a1)= 1.23 GeV. Chiral symmetry is spontaneously broken and it breaks down to the isospin symmetry: The Goldstone bosons are the 3 π in the case of 2 flavors and the 8 members of the meson octet in the case of 3 flavors.

( ) ( ) ( )V

L R

SU SU SU 2 2 2 → ×

Hadron Physics 21 Diego Be(oni

Hadron Physics 22

Theoretical Approaches to non-perturbative QCD

• Potential models. Bound systems of heavy quarks can be treated in

the framework of non-relativistic potential models, with forms which reproduce the asymptotic behaviour of QCD. Masses and widths are

• btained by solving Schrödinger’s equation.
• Lattice QCD (LQCD)

– The QCD equations of motions are discretized on a 4-dimensional space-time lattice and solved by large-scale computer simulations. – Enormous progress in recent years (e.g. gradual transition from quenched to unquenched calculations). – Ever increasing precision, thanks also to sinergies with EFT.

• Effective Field Theories (EFT)

They exploit the symmetries of QCD and the existence of hierarchies

• f scales to provide effective lagrangians that are equivalent to QCD

for the problem at hand. – With quark and gluon degrees of freedom (e.g. Non Relativistic QCD or NRQCD) – With hadronic degrees of freedom (e.g. Chiral Perturbation Theory).

Diego Be(oni

Hadron Physics 23

The Non-Relativistic Potential

The functional form of the potential is chosen to reproduce the known asymptotic properties of the strong interaction.

• At small distances asymptotic freedom, the potential is

coulomb-like:

• At large distances confinement:

r r r V

s r

) ( 3 4 ) ( α − ⎯ ⎯→ ⎯ →

kr r V

r ⎯

⎯ → ⎯

∞ →

) (

Diego Be(oni

Hadron Physics 24

The Non-Relativistic Potential II

) ln( ) 3 2 11 ( 4 ) (

2 2

Λ − = µ π µ α

f s

n

nf = number of flavours Λ ~ 0.2 GeV QCD scale parameter k string constant (~ 1 GeV/fm)

Diego Be(oni

Hadron Physics 25

The Spin-Dependent Potential

T SS LS SD

V V V H + + = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ⋅ = dr dV dr dV r m S L V

S V c LS

3 2 ) (

2

• (

)

) ( 3 2

2 2 2 1

r V m S S V

V c SS

∇ ⋅ =

• (

)( )

[ ]

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − − ⋅ ⋅

2 2 2 2

1 12 ˆ ˆ 3 2 dr V d dr dV r m S r S r S V

V V c T

• spin-orbit

(fine structure) spin-spin (hyperfine structure) tensor VS and VV are the scalar and vector components of the non-relativistic potential

Diego Be(oni

Hadron Physics 26

The Spin-Dependent Potential II

• The Coulomb-like part of V(r) corresponds to one-gluon exchange

and contributes only to the vector part of the potential VV. The scalar part is due to the linear confining potential. This could in principle contribute to both VS and VV, but the fit to the χcJ masses suggests that the VV contribution is small.

• The charmonium mass spectrum can be computed also within the

framework of Lattice QCD (LQCD), which is essentially QCD applied to a discreet 4-dimensional space with given spacing a.

• Non Relativistic QCD (NRQCD) provides another framework for the

calculation of the heavy quarkonium spectrum. In NRQCD the various dynamical scales m, mv, mv2 in the production and decay processes are well separated.

Diego Be(oni

Effective Field Theories (EFT)

A non-relativistic bound state is characterized by at least three scales:

– mass m (hard) – momentum transfer mv (soft) – kinetic energy of the qq pair in the CMS E ∼ p2/m ∼ mv2 (ultrasoft)

Hierarchy of scales ⇒ substitute QCD with simpler, but equivalent, Effective Field Theory (EFT), i.e. a quantum field theory with the following properties:

• It contains the relevant degrees of freedom to describe

phenomena which occur in a certain limited range of energies and momenta.

• It contains an intrinsic energy scale Λ that sets the limit of

appicability of the EFT.

Hadron Physics 27 Diego Be(oni

Effective Field Theories (EFT)

• Heavy Quark Effective Theory (HQET) describes systems

with one heavy quark (qQ, Qq), characterized by scales m and ΛQCD. Integrate m out and build expansion in ΛQCD /m.

• Non Relativistic QCD (NRQCD) describes bound states of

two heavy quarks (QQ). Integrate out only m and leaves lower scales as dynamical degrees of freedom.

Hadron Physics 28 Diego Be(oni

Lattice QCD (LQCD)

The interac5on is discre5zed on a 3 (Space) + 1 (Time) dim. Labce e.g. ∂tφ → [φ(t+a) - φ(t-a)]/2a. Con5nuum results obtained by a → 0. LQCD formulated in Euclidean space-5me. LQCD is a first principles approach: only parameters inherent to QCD, i.e. αs and the quark masses. These nf+1 parameters are fixed by matching nf+1 low-energy quan55es to their experimental values.

Q (Mesons) Q Glueballs

Observables are calculated taking their expectation values in the path integral approach ⇒ take average of all possible “configurations” of gauge fields.

Hadron Physics 29 Diego Be(oni

The bb Spectrum from LQCD

• 0.5

0.5 1 1.5 2 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 V0(r)/GeV r/fm b =6.0 b =6.2 fit

G.S. Bali, K. Sc hilling and A.Wachte r, PRD56 (1997) 2566 G .S. Ba li, K. Sc hilling a nd A.Wac hte r, he p-ph/9611226

9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 n1S0 n3S1 n1P1 n3P0 n3P1 n3P2 e=0.495 e=0.40

The static potential derived from LQCD confirms the Coulomb + Confinement Ansatz

Hadron Physics 30 Diego Be(oni

QQ Potential from LQCD

• 3
• 2
• 1

1 2 3 4 0.5 1 1.5 2 2.5 3 [V(r)-V(r0)]r0 r/r0 Σg

+

Πu 2 mps mps + ms quenched κ = 0.1575

G . Ba li e t a l., h e p -la t/000301 2 SESAM a nd T L

χ

One-Gluon-Exchange Excited Gluon

In the quenched approximation sea quarks are neglected.

( )

r r r V

s

σ α + − = 3 4

Hadron Physics 31 Diego Be(oni

• Glueballs are the

excitation of the QCD vacuum

– Comparably easy to calculate – Lots of improvements in the last decade – Mainly due to

• anisotropic lattices
• improved actions

Morningstar und Peardon, PRD60 (1999) 034509 Morningstar und Peardon, PRD56 (1997) 4043

Glueballs

Hadron Physics 32 Diego Bettoni

Hadrons are very complicated

qq (q )(q ) q q + (q )g q + gg +

qq (qq)(qq) (qq)g

• Quarkmodels usually

account for qq states

• Other color neutral

configurations with same quantum numbers can (and will mix)

• Decoupling only possible for

– narrow states – vanishing leading qq term

Hadron Physics 33 Diego Bettoni

Definition of Hadron Configurations

SU(3)c symmetry tells us that

(3i+n)q (3j+n)q (k)g

is colour neutral i=1, j=n=k=0 baryon i=j=k=0, n=1 meson i=j=n=0, k>1 glueball i=j=0, n=1, k>1 meson hybrid i=1, j=n=0, k>1 baryon hybrid i=n=1, j=k=0 pentaquark i=j=k=0, n=2 four-quark i=j=k=0, n=3 or i=j=1, n=k=0 baryonium

Hadron Physics 34 Diego Bettoni

Classification (Close and Lipkin)

Exotics of the first kind External quantum numbers unambiguously incompatible with assignment to baryons or mesons B=1 - baryonlike

– Q>2, Q<-1, S<-3, S>0, I>3/2, ....

B=0 - mesonlike

– |Q|>1, I>1, |S|>2, |C|>2, |S-C|>1, ....

Hadron Physics 35 Diego Bettoni

Classification (Close and Lipkin)

Exotics of the second kind Combination of quantum numbers not allowed for leading Fock-term Only possible for B=0 – JPC = 0--, 0+-,1-+, 2+-, ... – cannot be formed by any unexcited qq-System

Hadron Physics 36 Diego Bettoni

Classification (Close and Lipkin)

Exotics of the third kind – Crypto-Exotics Internal exotic structure

– like gluonic excitations – like N-quarks

but no model free signature approach:

– overpopulation of hadron multiplets – unexpected masses and decay properties – a well understood conventional meson picture is mandatory

Hadron Physics 37 Diego Bettoni

Experimental Measurements

• Spectroscopy of QCD bound states. Precision measurement
• f particle spectra to be compared with theory calculations.

Identification of the relevant degrees of freedom. – light quarks, cc, bb – D meson – baryon

• Search for new forms of hadronic matter: hybrids,

glueballs, multiquark states ...

• Hadrons in nuclear matter. Origin of mass.
• Hypernuclei.
• Study of nucleon structure.

– Form Factors – PDF, GDA, TMD

• Spin physics.

Hadron Physics 38 Diego Be(oni

Experimental Techniques

e+e- collisions

direct formation two-photon production initial state radiation (ISR) B meson decay (BaBar, Belle(2), BESIII, CLEO(-c), LEP) + low hadronic background

+ high discovery potential

• direct formation limited to vector

states

• limited mass and width resolution

for non vector states

pp annihiliation

(LEAR, Fermilab E760/E835, PANDA)

• high hadronic background

+ high discovery potential + direct formation for all (non-exotic) states + excellent mass and width resolution for all states

Hadroproduction

(CDF, D0, Compass, LHC)

Electroproduction

(HERA, JLAB12)

Hadron Physics 39 Diego Be(oni

Hadron Production in e+e- Annihilation

Direct Forma5on

In e+e- annihilations direct formation is possible

• nly for states with the quantum numbers of the

photon JPC=1--: J/ψ, ψʹ and ψ(3770).

Diego Be(oni Hadron Spectroscopy 40

Hadron Production in e+e- Annihilation

Direct Forma5on Two-Photon Produc5on

Diego Be(oni Hadron Spectroscopy 41

J-even states can be produced in e+e- annihilations at higher energies through γγ collisions. The (cc) state is usually identified by its hadronic

• decays. The cross section for this process

scales linearly with the γγ partial width of the (cc) state.

• Like in direct formation, only JPC=1–

states can be formed in ISR.

• This process allows a large mass range

to be explored.

• Useful for the measurement of

R = σ(e+e-→hadrons)/σ(e+e-→µ+µ-).

• Can be used to search for new vector states.

Hadron Production in e+e- Annihilation

Direct Forma5on Two-Photon Produc5on Ini5al State Radia5on

Diego Be(oni Hadron Spectroscopy 42

Hadron Production in e+e- Annihilation

Direct Forma5on Two-Photon Produc5on Ini5al State Radia5on B-meson decay Double Charmonium

Diego Be(oni Hadron Spectroscopy 43

e+e- annihila5on provides a very favourable environment for the study of hadron spectroscopy

Hadron Physics 44

pp Annihilation

In pp collisions the coherent annihilation of the 3 quarks in the p with the 3 antiquarks in thep makes it possible to form directly states with all non-exotic quantum numbers. The measurement of masses and widths is very accurate because it depends only on the beam parameters, not on the experimental detector resolution, which determines only the sensitivity to a given final state.

Diego Be(oni

Hadron Physics 45

Experimental Method

( )

4 / 4 1 2

2 2 2 2 R R R

• ut

in BW

M E B B k J Γ + − Γ + = π σ

The cross section for the process: pp → R → final state is given by the Breit-Wigner formula: The production rate ν is a convolution of the BW cross section and the beam energy distribution function f(E,ΔE):

{ }

∫

+ Δ =

b BW E

E E dEf L σ σ ε ν ) ( ) , (

The resonance mass MR, total width ΓR and product of branching ratios into the initial and final state BinBout can be extracted by measuring the formation rate for that resonance as a function of the cm energy E.

Diego Be(oni

Hadron Physics 46

Example: χc1 and χc2 scans in Fermilab E835

χ1 χ2

Diego Be(oni

Hybrids and Glueballs in pp Annihilation

Gluon rich process creates gluonic excitation in a direct way

– cc requires the quarks to annihilate (no rearrangement) – yield comparable to charmonium production – even at low momenta large exotic content has been proven – Exotic quantum numbers can only be achieved in production mode

p p

_

G M p M H p

_

p M H p

_

p p

_

G p p

_

H p p

_

H

Production all JPC available Formation

• nly selected JPC

nng ssg/ccg

Hadron Physics 47 Diego Be(oni

Selected Hot Topics

Heavy Quarkonium The X, Y, Z States Open Charm Baryons Electromagne5c Form Factors

Hadron Physics 49

Heavy quarkonia are non rela5vis5c bound states mul5scale systems:

2

v m v m m

Q Q Q

>> >> GeV m GeV m m

c b QCD Q

5 . 1 5 ≈ ≈ Λ >>

The mass scale is perturba5ve: The system is non rela5vis5c:

3 . 1 .

2 2

≈ ≈

c b

v v

The structure of separated energy scales makes quarkonium an ideal probe of (de)confinement. Quarkonia probe the perturba5ve, non perturba5ve and transi5on regimes.

Diego Be(oni

Charmonium Spectrum I

Hadron Physics 50

All 8 states below open charm threshold are well established experimentally, although some precision measurements still needed (e.g. ηc(2S), hc) The region above threshold still to be understood:

• find missing states (e.g. D-wave)
• understand nature of newly

discovered states (e.g. X Y Z) Hyperfine splitting of quarkonium states gives access to VSS component of quark potential model

Diego Be(oni

Charmonium Spectrum II

Hadron Physics 51 Diego Be(oni

New Quarkonium States Below Open Flavor Threshold

Hadron Physics 52 Diego Be(oni

Hadron Physics 53

The ηc(21S0)

Belle

PDG 2016 M(ηcʹ) = 3639.2 ± 1.2 MeV/c2 Γ(ηʹc) = 11.3 +3.2

• 2.9 MeV

ΔMhf(2S)cc ≡ M(ψ(2S)) - M(ηc(2S)) = 46.9 ± 1.3 MeV

Diego Be(oni

Hadron Physics 54

• Quantum numbers JPC=1+-.
• The mass is predicted to be within a few MeV of the center of gravity of the

χc(3P0,1,2) states

• The width is expected to be small Γ(hc) ≤ 1 MeV.
• The dominant decay mode is expected to be ηc+γ, which should account

for ≈ 50 % of the total width.

• It can also decay to J/ψ:

J/ψ + π0 violates isospin J/ψ + π+π- suppressed by phase space and angular momentum barrier

The hc(1P1)

9 ) ( M 5 ) ( M 3 ) ( M M

2 1 cog

χ χ χ + + =

Diego Be(oni

The hc(1P1)

) )( ( '

c c

h e e γη γγ π ψ → → →

− +

The ψ' decay mode is isospin viola5ng The CLEO experiment was able to find it with a significance of 13 σ in ψ’ decay by means of an exclusive analysis. The width and the BF ψ’→π0hc were not measured. A similar analysis, with higher sta5s5c, was also done by BES

Center of gravity of P-states

−0.10±0.13±0.18MeV/c2

Hadron Physics 55 Diego Be(oni

Hadron Physics 56

Jingzhi Zhang – Charm 2013

Diego Be(oni

Hadron Physics 57

X(3823)

B àχc1γK M = 3823.1 ± 1.8 ± 0.7 MeV/c2 Γ < 24 MeV 711 fb-1 3.8 σ

• V. Bhardwaj et al.(Belle Collab.), Phys. Rev. Lett. 111, 032001

Measured mass and width consistent with predicted values for ψ2(1D) (1 D2)

Diego Be(oni

Bottomonium Specroscopy

Hadron Physics 58

Agreement with theore5cal predic5ons be(er because of:

• higher b quark mass
• lower value of αs.
• dominance of Coulomb term

in the poten5al

Diego Be(oni

The ηb(1S0) Bottomonium State

The ϒ(13S1) state of bo(omonium was discovered in 1977. The ground state spin-singlet partner, ηb(11S0), has been found only recently by the BaBar Collabora5on by studing Υ(3S) → γ ηb(1S) [PRL101,071801,2008] Then confirmed in Υ(2S) → γ ηb(1S) [PRL103, 161801,2009] and by CLEO [PRD8,031104,2010] Mass of the ηb(1S):

• Peak in γ energy spectrum at
• Corresponds to ηb mass 9391.1±3.1 MeV/c2
• The hyperfine (Υ(1S)-ηb(1S)) mass splibng is 69.9 ± 3.1 MeV/C2

The observa5on of the ηb is an important valida5on of Labce QCD predic5ons

Hadron Physics 59 Diego Be(oni

The hb(1P1) Bottomonium State

Hadron Physics 60 Diego Be(oni

Hadron Physics 61 Diego Be(oni

Evidence for Υ(3S) → π0hb(1P)

Hadron Physics 62

( ) ( )

2

/ 1 2 9902 c MeV h M

b

± ± =

Sta5s5cal significance 3.1 σ

( )

( ) ( )

4

10 9 . 1 . 1 3 . 4 ) 3 (

−

× ± ± = → × → Υ

b b b

h B h S B γη π

10721 ± 2806 events

Diego Be(oni

hb → γηb at Belle

Hadron Physics 63

BR (hb → γηb) = (49.8 ± 6.8 +10.9

• 5.2) %

Diego Be(oni

The Y(1D)

Hadron Physics 64

) 1 ( ) 1 ( ) 3 (

3

S D S

J

Υ → Υ → Υ

− +π

γγπ γγ

CLEO

( ) (

)

2 2 3

/ 5 . 8 . 5 . 10164 1 c MeV D M ± ± =

Diego Be(oni

The χb(3P)

χb(3P) χb(3P) → Υ(1S) + γ χb(3P) → Υ(2S) + γ

M(χb(3P)) = 10.539 ± 0.004 (stat) ± 0.008 (syst) GeV/c2

Hadron Physics 65 Diego Be(oni

The XYZ States

Hadron Physics 66 Diego Be(oni

The XYZ States

Hadron Physics 67 Diego Be(oni

Hadron Physics 68

The X(3872) Discovery

New state discovered by Belle in the hadronic decays of the B-meson: B±→K± (J/ψπ+π-), J/ψ→µ+µ- or e+e- M = 3872.0 ± 0.6 ± 0.5 MeV Γ< 2.3 MeV (90 % C.L.)

( )

( )

.) . % 90 ( 89 . / ) 3872 ( ) 3872 (

1

L C J X X

c

< → Γ → Γ

− +

ψ π π γχ

Diego Be(oni

Hadron Physics 69

The X(3872) Confirmation

BaBar CDF D0

Diego Be(oni

The X(3872) at LHCb

Hadron Physics 70

JPC = 1++

Confirmed from analysis of angular correla5ons in B+ → X(3872)K+ → π+π-J/Ψ, J/Ψ→μ+μ- arXiv:1504.06339v1

Diego Be(oni

The X(3872) at BES III

Hadron Physics 71

ISR ψ’ signal is used for rate, mass, and mass resolution calibration. N(ψ’)=1242 ; Mass=3685.96±0.05 MeV; σM=1.84 ±0.06 MeV N(X(3872))=15.0±3.9 5.3σ M(X(3872)) = 3872.1±0.8±0.3 MeV [PDG: 3871.68 ±0.17 MeV]

BESIII preliminary

• C. Yuan – Charm 2013

Diego Be(oni

Hadron Physics 72

What is the X(3872) ?

• Mass: Very close to D0D*0 threshold
• Width: Very narrow, < 1.2 MeV
• Small binding energy implies huge separation ∼ 5 fm
• JPC=1++ [LHCb]
• Production

– in pp/pp collison – rate similar to charmonia – In B decays – KX similar to cc, K*X smaller than cc – Y(4260)àγ+X(3872) [BESIII]

• Decay BR: open charm ~ 50%, charmonium~O(%)
• Nature (very likely exotic)

– Loosely D0D*0 bound state (like deuteron?)? – Mixture of excited χc1 and D0D*0 bound state? – Many other possibilities (if it is not χ’c1, where is χ’c1?).

Diego Be(oni

Hadron Physics 73

Y(4260)

Discovered by BaBar in ISR events: e+e-→ γISRπ+π-J/ψ

From PDG:

MeV c MeV M 12 108 / 9 4250

2

± = Γ ± =

JPC = 1--

Confirmed by CLEO, CLEO III, Belle, BESIII Weak coupling consistent with hybrid meson. Shows up as very small maximum near the deep minimum between conventional charmonium states ψ(4160) and ψ(4415)

Diego Be(oni

Z+(4430), Z1

+(4050), Z2 +(4250)

Hadron Physics 74

Z+(4430) →ψ(2S)π+ Z1

+(4050) →χc1π+, Z2 +(4250) →χc1π+

Not confirmed by BaBar that also studied the J/ψπ-K+ and J/ψπ-K0

s channels.

The J/ψπK final state was also studied by Belle, who did not find any evidence of Z. Belle confirmed the Z in a Dalitz reanalysis. Not confirmed by BaBar which did not find evidence of a signal in the exo5c χc1π+ channel.

Diego Be(oni

Z-(4430) at LHCb

Hadron Physics 75

B0 → K+ψ(2S)π- M = 4475 ± 7 +15

• 25 MeV

Γ = 172 ± 13 +37

• 34 MeV

JP = 0+

Diego Be(oni

Zb(10610) and Zb(10650)

Hadron Physics 76

The Zb

+(10610) and Zb +(10650) lie very close to the

BB* and B*B* thresholds, respectively. Molecular states ?

• Zb

+(10610) and Zb +(10650)

• Discovered by Belle in 2011 in π+π-

transi5ons from Υ(5S).

• Both decay to Υ(nS)π+ and hb(nP)π+.

5σ evidence for neutral isospin partner of Zb

+(10610).

• Minimal quark content bbud

Diego Be(oni

Hadron Physics 77

M = 3899.0±3.6±4.9 MeV Γ = 46±10±20 MeV 307 ± 48 events >8σ Y(4260) →π+π-J/ψ, J/ψ→l+l- 1477 events – 525 pb-1 σ = (62.9 ± 1.9 ± 3.7) pb consistent with Y(4260) produc5on A structure observed in the J/ψπ± mass spectrum Minimal quark content bbud

Zc(3900)±

Zc

+(3900)

Diego Be(oni

Zc

+(3900)

Hadron Physics 78

Belle

• C. Yuan – Charm 2013

Belle with ISR: 1304.0121 M = 3894.5±6.6±4.5 MeV Γ = 63±24±26 MeV 159 ± 49 events >5.2σ CLEOc data at 4.17 GeV: 1304.3036 M = 3885±5±1 MeV Γ = 34±12±4 MeV 81 ± 20 events 6.1σ

Diego Be(oni

Zc

0(3900) in e+e- → π0π0J/ψ

Hadron Physics 79

• H. Peng – ICHEP2014

Diego Be(oni

Hadron Physics 80

e+e-→ πZc(4020)àπ+π-hc(1P)

Ecm=4.26 GeV Ecm=4.36 GeV

Simultaneous fit to 4.26/4.36 GeV data and 16 ηc decay modes. 6.4σ M(Zc(4020)) = 4021.8±1.0±2.5 MeV; Γ(Zc(4020)) = 5.7±3.4±1.1 MeV

N= 64±19 N= 56±17

BESIII preliminary

• C. Yuan – Charm 2013

Diego Be(oni

Fit to π± recoil mass yields 401±47 Zc(4025) events. >10σ M(Zc(4025)) = 4026.3±2.6±3.7 MeV; Γ(Zc(4025)) = 24.8±5.6±7.7 MeV

Hadron Physics 81

e+e-→ πZc(4025) àπ- (D*D*)++c.c.

BESIII: 1308.2760

Diego Be(oni

The LHCb Pentaquark

Diego Be(oni Hadron Physics 82

M = 4449.8±1.7±2.5 MeV Γ = 39±5±19 MeV M = 4380±8±29 MeV Γ =205±18±86 MeV

Λ0

b → P+ c K- J/ψpK-

Hadron Physics 83

Eric Braaten – Charm 2013

Diego Be(oni

Hadron Physics 84

Eric Braaten – Charm 2013

Diego Be(oni

Open Charm

Interest of charm

• Strong interactions

– QCD laboratory – Intermediate case between heavy and light quarks – Interesting spectroscopy – Strong decay modes

• Weak interactions

– Complementary to measurements with b quarks – Mixing and CP violation – Possible window to physics beyond the Standard Model

Hadron Physics 85 Diego Be(oni

Charm Meson Spectroscopy

Hadron Physics 86

• Ground states (D, D*) and two of the 1P states

D1(2420) and D2

*(2460) experimentally well

established since they are narrow.

• Broad L=1 states D0

*(2400) and D1’(2430)

found by BaBar and Belle in exclusive B decays

• Babar found 4 new states decaying to

Dπ and D*π.

Diego Be(oni

D mesons at LHCb

Hadron Physics 87 Diego Be(oni

Ds States

For the states c(u/d) theory and experiment were in agreement. The quark model describes the spectrum of heavy-light systems and it was expected to be able to predict unobserved excited DS(cs) mesons with good accuracy

DS DS* DS1 DS2

• B. Aubert et al., PRD74, 032007 (2006).

Hadron Physics 88 Diego Be(oni

Ds States

The discovery of the new DSJ states has brought into ques5on poten5al models

Two new states DS(2317) and DS(2460) were discovered in e+e− → cc events, then observed in B decays by Babar, Belle and CLEO The iden5fica5on of these states as the 0+ and 1+ cs states is difficult within the poten5al model DS DS* DS1 DS2 DS(2317) DS(2460) DS(2317)

CLEO

DS(2460)

Hadron Physics 89 Diego Be(oni

Ds States

DS DS* DS1 DS2 DS(2317) DS(2460)

The discovery of the new DSJ states con5nued …

DS(2860) DS(2710)

Belle Collab, PRL 100 (08) 092001

DS(2860) DS(2710)

Hadron Physics 90 Diego Be(oni

Ds States

The assignment of the q.n. to the DS(2710) was possible thanks to an analysis performed by BaBar studying DK, D*K final states. In the same analysis another broad structure in the D*K distribu5on DSJ(3040) DS DS* DS1 DS2 DS(2317) DS(2460) DS(2860) DS(2710) DSJ(3040) There is a problem for the poten5al models in describing excited states

Hadron Physics 91 Diego Be(oni

Strange and Charmed Hyperons

Hadron Physics 92 Diego Be(oni

Strange and Charmed Baryons

Hadron Physics 93 Diego Be(oni

Hadron Physics 94

Hypernuclear Physics

Hypernuclei, systems where one (or more) nucleon is replaced by one (or more) hyperon(s) (Y), allow access to a whole set of nuclear states containing an extra degree of freedom: strangeness.

• Probe of nuclear structure and its possible modifications due to the

hyperon.

• Test and define shell model parameters.
• Description in term of quantum field theories and EFT.
• Study of the YN and YY forces (single and double hypernuclei).
• Weak decays (Λ→πN suppressed, but ΛN→NN and ΛΛ→NN

allowed ⇒ four-baryon weak interaction)

• Hyperatoms
• Experimentally: in 50 years of study 35 single, 6 double hypernuclei

established

Diego Be(oni

Ξ- capture: Ξ- p → ΛΛ ΛΛ + 28 MeV

Ξ-

3 GeV/c Kaons

_ Ξ Λ Λ

trigger

p _

2. Slowing down and capture

• f Ξ- in

secondary target nucleus 1. Hyperon- antihyperon production at threshold +28MeV

γ

3.

γ-spectroscopy

with Ge-detectors

γ Pro Product ction of Double Hyp ypern rnucl clei

Ξ-(dss) p(uud) → Λ(uds) Λ(uds)

D.Be(oni PANDA at FAIR 95

1300 Hz 8000 / month 80 / month 5600 / day

Hadron Physics 96

Introduction

( ) ( )

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + =

ν µν µ µ

σ κ γ q i q F M q F e J

2 2 2 1

2

p0 p k kʹ jµ Jµ

1 ) ( ) ( 1 ) ( 1 ) (

2 1 2 1

= = = =

n n p p

F F F F Dirac and Pauli Form Factors

Diego Be(oni

Hadron Physics 97

2 1 2 2 2 1

4 F F G F M q F G

M E

κ κ + ≡ + ≡

• GE and GM are Fourier transforms of nucleon charge and magnetization

density distributions (in the Breit Frame).

• Spacelike form factors are real, timelike are complex.
• The analytic structure of the timelike form factors is connected by

dispersion relations to the spacelike regime.

• By definition they do not interfere in the expression of the cross section,

therefore, in the timelike case, only polarization observables allow to get the relative phase.

Sachs Form Factors

Diego Be(oni

Hadron Physics 98

N N e e + → +

− +

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + + =

* 2 2 2 * 2 2 2

sin ) ( 4 ) cos 1 ( ) ( 4 θ θ β α Ω σ s G s m s G s C d d

E N M

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + =

2 2 2 2

) ( 2 ) ( 3 4 s G s m s G s C

E N M

πβ α σ

2 >

= Q s

p p e+ e- θ*

Diego Be(oni

Hadron Physics 99

) (GeV s

C is the Coulomb correction factor, taking into account the QED coulomb interaction. Important at threshold.

y

e C

−

− = 1 1

s M y

N

β πα 2 =

β 1

2

4 ⎯

⎯ ⎯ → ⎯

→

N

M s

C σ finite

( )

nb M G M M

N E N N

1 . ) 4 ( 4 4

2 2 2 3 2 2

≈ = α π σ There is no Coulomb correction in the neutron case.

Diego Be(oni

Hadron Physics 100

Form Factor Properties

• At threshold GE=GM by definition, if F1 and F2 are analytic functions

with a continuous behaviour through threshold. GE (4mp

2) = GM (4mp 2)

• Timelike GE and GM are the analytical continuation of non spin flip

and, respectively, spin flip spacelike form factors. Since timelike form factors are complex functions, this continuity requirement imposes theoretical constraints.

• Two-photon contribution can be measured from asymmetry in

angular distribution.

Diego Be(oni

Hadron Physics 101

Form Factor Properties

• Perturbative QCD and analyticity relate timelike and

spacelike form factors, predicting a continuous transition and spacelike-timelike equalitity at high Q2.

• At high Q2 PQCD predicts:
• Naïve prediction for the neutron:

6 2 2 2 2 4 2 2 2 1

) ( ) ( ) ( ) ( Q Q Q F Q Q Q F

s s

α α ∝ ∝

25 .

2 2

= ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ≈

u d p M n M

q q G G

Diego Be(oni

Timelike FF: Some Open Questions

• Unpolarized measurements only yield moduli of FF
• Proton

– Due to the low value of the cross sections and the consequent limited statistics, most experiments could not determine |GM| and |GE| separately from the analysis of the angular distributions, but determined an effective FF. – Phases of FF unknown – Measurements limited to q2 < 20 GeV2.

• Neutron

– basically only one experiment at low q2 (FENICE)

• Other baryon FF measurements scarce

Hadron Physics 102 Diego Be(oni

Proton Timelike Form Factor

Diego Be(oni Hadron Physics 103

Proton Spacelike Form Factors

Diego Be(oni Hadron Physics 104

( )

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − × ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω 2 sin 2 2 cos 4

2 2 2 1 2 2 2 2 2 2 2 2 2 1

θ κ θ κ σ σ F F M q F M q F d d d d

Rutherford

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + + + × ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω 2 sin 2 2 cos 1

2 2 2 2 2

θ τ θ τ τ σ σ

M M E Rutherford

G G G d d d d ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + + + × ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω 2 tan 2 1

2 2 2 2

θ τ τ τ σ σ

M M E Mott

G G G d d d d

Rosenbluth Formula

2 2

4M q = τ

e- p → e- p

( ) ( )

2 2

q G G q G G

M M E E

= =

( ) ( ) ( ) ( )

91 . 1 79 . 2 1 − = + = = =

n M p M n E p E

G G G G

( ) ( )

2 tan 2

2 2

θ σ σ q B q A d d d d

Mott

+ = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Ω Rosenbluth Plot

Hadron Physics 105 Diego Be(oni

Nucleon Spacelike Form Factors

Diego Be(oni Hadron Physics 106

( ) ( ) ( ) ( ) ( )

2 2 2 2 2

= = = = q G q G q G q G q G

n E n n M p p M p E

µ µ

Hadron Physics 107 Diego Be(oni

Hadron Physics 108 Diego Be(oni

Hadron Physics 109 Diego Be(oni

Hadron Physics 110 Diego Be(oni

Hadron Physics 111 Diego Be(oni

Hadron Physics 112 Diego Be(oni

Hadron Physics 113 Diego Be(oni

Hadron Physics 114 Diego Be(oni

Hadron Physics 115 Diego Be(oni

Hadron Physics 116 Diego Be(oni

Hadron Physics 117 Diego Be(oni

Hadron Physics 118 Diego Be(oni

Hadron Physics 119 Diego Be(oni

Hadron Physics 120 Diego Be(oni

Hadron Physics 121 Diego Be(oni

Proton Radius Puzzle

Hadron Physics 122 Diego Be(oni

Outlook and Conclusions

Experimental Facili5es Conclusions

The Facilities

• The LHC Experiments
• BES III at BEPC
• Belle 2
• JLAB 12 GeV upgrade
• PANDA at FAIR
• Compass @ CERN
• ELSA@Bonn
• MAMI, MESA

Hadron Physics 124 Diego Be(oni

Hadron Physics 125

LHC Experiments

ATLAS CMS LHCB

Diego Be(oni

Hadron Physics 126

BEPCII/BESIII

Diego Be(oni

BESIII Detector

Hadron Physics 127

1.3 × 109 J/ψ 0.5 × 109 ψ(2S) ψ(3770) 4.23, 4.26, 4.36 GeV

Diego Be(oni

Hadron Physics 128 Diego Be(oni

Hadron Physics 129 Diego Be(oni

Hadron Physics 130 Diego Be(oni

The JLAB 12 GeV Upgrade

Hadron Physics 131 Diego Be(oni

The 12 GeV Equipment

Hadron Physics 132

• M. Battaglieri – Erice 2011

Diego Be(oni

Hadron Physics 133

• M. Battaglieri – Erice 2011

Diego Be(oni

The FAIR Complex

Primary Beams

• All elements up to Uranium
• Factor 100-1000 over

present intensity

• 50ns bunching

Secondary Beams

• Rare isotope beams up to a

factor of 10 000 in intensity

• ver present
• Low and high energy

antiprotons

• Beam cooling
• Rapidly cycling superconducting magnets
• Narrow bunching of beams

Key Technologies

Storage and Cooler Rings

• Rare isotope beams
• e-– Rare Isotope collider
• 1011 stored and cooled

antiprotons for Antimatter creation

Rare Isotope Production Target Antiproton Production Target

Hadron Physics 134 Diego Be(oni

Hadron Physics 135

High luminosity mode High resolution mode

Nstored = 1010 p dp/p ~ 3×10-5 (electron cooling)

• Lumin. = 1031 cm-2 s-1

Nstored = 1011 p

• Lumin. = 2 x 1032 cm-2 s-1

dp/p ~ 10-4 (stochastic cooling) Production rate 2x107/sec Pbeam = 1.5 - 15 GeV/c Internal Target 4×1015 cm-2

High-Energy Storage Ring Modularized Start Version (MSV0-3) L ~ 1031cm-2s-1 Δp/p ~ 5 × 10-5

Diego Be(oni

PANDA Spectrometer

Hadron Physics 136 Diego Be(oni

Diego Be(oni Hadron Physics 137

Conclusions

• Hadron spectroscopy is an invaluable tool for a deeper understanding of

the strong interaction and QCD.

• Exciting new experimental results achieved over the past two decades

thanks to many experiments at hadron machines and e+e- colliders. – Quarkonium states below threshold – X, Y, Z states reveal new sector of QCD spectrum – Open charm states

• Progress in theory

– Lattice QCD – Effective Field Theories

• For the near and medium term future first rate results are expected from

– LHC – e+e- colliders (BES III, Belle2). – JLAB 12 GeV (CLAS12 and GlueX) – PANDA at FAIR

• Complementary approaches

Hadron Physics 138 Diego Be(oni