Theory Castello di Trento (Trint), watercolor 19.8 x 27.7, painted - - PowerPoint PPT Presentation

Barbara Pasquini / Marc Vanderhaeghen

Theory Summary

ECT*

EUROPEAN CENTRE FOR THEORETICAL STUDIES IN NUCLEAR PHYSICS AND RELATED AREAS TRENTO, ITALY

Institutional Member of the European Expert Committee NUPECC

Castello di Trento (“Trint”), watercolor 19.8 x 27.7, painted by A. Dürer on his way back from Venice (1495). British Museum, London

The Proton Mass: At the Heart of Most Visible Matter

Trento, April 3 - 7, 2017

Main Topics

Hadron mass decomposition in terms of constituents: Uniqueness of the decomposition, Quark mass, and quark and gluon energy contribution, Anomaly contribution, ... Hadron mass calculations: Lattice QCD (total & individual mass components), Approximated analytical methods, Phenomenological model approaches, ... Experimental access to hadron mass components: Exclusive heavy quarkonium production at threshold, nuclear gluonometry through polarized nuclear structure function, …

Confjrmed keynote speakers

Alexandrou Constantia (Cyprus University), Brodsky Stan (SLAC), Burkhardt Matthias (New Mexico State University), Camalich Jorge Martin (CERN), Chen Jian-Ping (Jefferson Lab), Chudakov Eugene (Jefferson Lab), Cloët Ian (Argonne National Lab), de Teramond Guy (University Costa Rica), Deshpande Abhay (Stony Brook University), Eichmann Gernot (Giessen University), Gao Haiyan (Duke University), Hafjdi Kawtar (Argonne National Lab), Hoelbling Christian (University of Wuppertal), Lin Huey-Wen (Michigan State University), Liu Keh-Fei (University of Kentucky), Lorcé Cédric (École Polytechnique, Palaiseau), Mulders Piet (Vrije University of Amsterdam), Papavassiliou Joannis (Valencia University), Pascalutsa Vladimir (Johannes Gutenberg University of Mainz), Peng Jen-Chieh (University Illinois Urbana-Champaign), Richards David (Jefferson Lab), Roberts Craig (Argonne National Lab), Scherer Stefan (Johannes Gutenberg University of Mainz), Slifer Karl (University of New Hampshire).

Organizers

Zein-Eddine Meziani (Temple University) Barbara Pasquini (University of Pavia) Jianwei Qiu (Jefferson Lab) Marc Vanderhaeghen (Universität Mainz) Director of the ECT*: Professor Jochen Wambach (ECT*) The ECT* is sponsored by the “Fondazione Bruno Kessler” in collaboration with the “Assessorato alla Cultura” (Provincia Autonoma di Trento), funding agencies of EU Member and Associated States and has the support of the Department of Physics of the University of Trento. For local organization please contact: Gianmaria Ziglio - ECT* Secretariat - Villa Tambosi - Strada delle Tabarelle 286 - 38123 Villazzano (Trento) - Italy Tel.:(+39-0461) 314721 Fax:(+39-0461) 314750, E-mail: ect@ectstar.eu or visit http://www.ectstar.eu

2

scales in QCD

Ø Only apparent scale in chromodynamics is mass of the quark field Ø In connection with everyday matter, that mass is 1/250th of the natural (empirical) scale for strong interactions,

• viz. more-than two orders-of-magnitude smaller

Ø Quark mass is said to be generated by Higgs boson. Ø Plainly, however, that mass is very far removed from the natural scale for strongly-interacting matter Ø Nuclear physics mass-scale – 1 GeV – is an emergent feature of the Standard Model – No amount of staring at LQCD can reveal that scale Ø Contrast with quantum electrodynamics, e.g. spectrum of hydrogen levels measured in units of me, which appears in LQED

• C. Roberts

its absolute value is NOT explained by the Standard Model

3

Scales in strong interactions

Resolution

Complexity

Simplicity

Hot and dense quark-gluon matter

Hadron structure Nuclear structure Nuclear reactions Nuclear astrophysics Applications of nuclear science

Hadron-Nuclear interface

4

Scale invariance of QCD (classical)

in absence of quark masses Theory is invariant under scale transforma=on

x → eλx

Noether current dilata=on current: energy momentum tensor

sµ = T µνxν

scale invariant theory: dilata=on current is conserved

0 = ∂µsµ = T µ

µ

Scale-invariant classical theory: energy-momentum tensor is traceless

5

Scale/trace anomaly in QCD

Quantum (loop) effects lead to a non-zero trace of energy-momentum tensor Quantum loop correc=ons: running coupling -> dimensional transmuta=on

β(g) = −b g3 16π2 + ..., b = 11 − 2 3Nf

T µ

µ = β(g)

2g Ga

αβGaαβ +

X

l=u,d,s

ml(1 + γml)¯ ql¯ ql + X

h=c,b,t

mh(1 + γmh) ¯ Qh ¯ Qh

at low energies: heavy quarks decouple

X

h=c,b,t

mh ¯ Qh ¯ Qh → −2 3Nh g2 32π2 Ga

αβGaαβ + ...

T µ

µ =

˜ β(g) 2g Ga

αβGaαβ +

X

l=u,d,s

ml(1 + γml)¯ ql¯ ql

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Mass of hadrons

2M 2 = hP| ˜ β(g) 2g Ga

αβGaαβ|Pi + hP|

X

l=u,d,s

ml(1 + γml)¯ ql¯ ql|Pi

hP|T µν|Pi = 2P µP ν

In chiral limit all of hadron mass is due to the trace anomaly Quark contribuEons to hadron mass: sigma-terms For pion: zero mass in chiral limit implies cancella=on between different components: dynamical chiral symmetry breaking LaIce QCD, dispersion rela=ons, ChPT Physics pictures (non-perturba=ve models) how hadron masses can be understood: Shed light on the non-trivial nature of bound state in QCD / confinement effec=ve degrees of freedom at hadronic scale / relevant symmetries, breaking paQerns

• C. Roberts
• D. Binosi, I. Cloët, J. Papavassiliou, C. Roberts
• Dyson-Schwinger Eq.
• Holographic QCD
• Rest frame decomposi=ons (e.g bag, soliton,…models)
• S. Brodsky, G. de Teramond
• X. Ji

σud, σs

• Partonic interpreta=ons
• C. Lorcé, L. Mantovani, M. Burkardt
• Instanton liquid
• P. Faccioli
• rela=vis=c bound states
• P. Hoyer

7

Models / Interpretations

8

Light quarks and confinement

Understanding the origin and absence of mass in QCD likely inseparable from understanding of confinement

• G. Bali et al., PoS LAT2005 (2006) 308
• C. Roberts

9

Continuum truncation: Dyson-Schwinger (I)

• D. Binosi, I. Cloët, J. Papavassiliou, C. Roberts

dynamical confinement: massless gauge bosons acquire a mass (IR cut-off in QCD) QCD effec=ve charge: Coupling possesses IR fixed point

10

Continuum truncation: Dyson-Schwinger (II)

• D. Binosi, I. Cloët, J. Papavassiliou, C. Roberts

dynamical chiral symmetry breaking (quark-gluon dynamics):

• rigin of mass

pion exists if and only if mass is dynamically generated PS Bethe-Salpeter amplitude in pseudo scalar channel: the dynamically generated mass of the two fermions is precisely cancelled by the aQrac=ve interac=ons between them

Continuum truncation: Dyson-Schwinger (III)

• I. Cloët, C. Roberts

pion DA can be obtained as projec=on of pion’s Bethe-Salpeter amplitude onto light-front

12

Holographic QCD

S.J. Brodsky, G. de Teramond

13

Holographic QCD

S.J. Brodsky, G. de Teramond

14

Holographic QCD

S.J. Brodsky, G. de Teramond

supersymmetric and superconformal constraints

• n meson and baryon masses

15

Proton mass decompositions

• X. Ji, J.W. Qiu

16

Proton mass decompositions

• X. Ji, J.W. Qiu

Quark Spin Quark OAM Quark spin-orbit correlation

Chiral-odd EMT Parity-odd EMT

Transverse spin-orbit correlations

Partonic interpretations

• C. Lorcé

Kinetic EMT Belinfante EMT EOM

Interpretation in scalar diquark model

• L. Mantovani

in absence of gluons: Kinetic OAM = Jaffe-Manohar OAM

Kinetic Canonical

Quark OAM from Wigner distributions

• M. Burkardt

21

What is known or can be learned from lattice QCD / phenomenology ?

Hadron masses (lattice)

• C. Alexandrou, C. Hoelbling, H.W. Lin, K.F. Liu, D. Richards, Y. Yang

23

Quark mass contributions (lattice)

• C. Alexandrou, C. Hoelbling, H.W. Lin, K.F. Liu, D. Richards, Y. Yang

laIce calcula=ons at physical point (solid symbols) New preliminary BMW results:

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Nucleon spin (lattice)

• C. Alexandrou

X

q

hxiq ⇡ X

q

2Jq

Gluonic contribu=on calculated on laIce !

Bg(0) = 0

25

pion-nucleon 𝜏-terms: ChPT

J.M. Alarcon

~ 3 𝜏 tension between recent laIce and ChPT / DR

26

pion-nucleon 𝜏-terms: dispersion theory

J.Ruiz de Elvira

27 J.M. Alarcon

pion-nucleon 𝜏-terms: ChPT

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Nucleon structure corrections to precision observables

• V. Pascalutsa

γ

γ

l

l

p

p

1S-HFS measurement in H

with 1 ppm accuracy

µ X

forthcoming PSI

relative contribution (✕10-3) relative uncertainty X=p (Zemach)

• 7,36

140 ppm X=p (recoil) 0,8476 0.8 ppm X=p, πN,… (polarizability) 0,363 86 ppm total

• 6,149

164 ppm

Antognini(2016) Carlson, Nazaryan, Griffioen(2011) Tomalak et al.(2016)

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threshold photoproduction of J/ψ on nucleons

heavy quarkonium: color dipole interac=on with hadrons may be es=mated from its chromoelectric polarizability (QCD van der Waals force)

• 2-gluon exchange
• at very large distances: interac=on dominated by pions

calculated from trace of energy momentum tensor

Peskin (1979); Voloshin, Zakharov (1980); Fujii, Kharzeev (1999)

quarkonium-proton interac=on at low energies probes distribu=on of mass in proton

• D. Kharzeev

θµ

µ

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J/ψ-p scattering amplitude, existence of J/ψ-nuclear bound states ?

threshold 𝜔-p scaQering amplitude: if 𝜔-p aQrac=on is strong enough

Brodsky, Schmidt, de Teramond (1990); Wason (1991); Luke, Manohar, Savage (1992)

Tψp = 8π(M + Mψ)aψp

s-wave 𝜔-p scaQering length (posi=ve: aQrac=on) forma=on of 𝜔-nuclear bound states possible

Bψ ' 8π(M + Mψ)aψp 4MMψ ρnm

in linear density approxima=on 𝜔-nuclear maQer binding energy

Kaidalov, Volkovitsky (1992)

many es=mates:

• perturba=ve calcula=on of chromoelectric polarizability (2-gluon exchange)

Bψ ∼ 10 MeV

• laIce QCD:

Beane et al. (2015)

Bψ ≤ 40 MeV (mπ ∼ 805 MeV)

H.W. Lin

31

forward J/ψ - p scattering (I)

spin-averaged amplitude: kinema=c variable:

p p J/ψ J/ψ

Tψp(ν)

ν ≡ p q = s − u 4

unitarity

Im Tψp(ν) = 2√s qψp σtot

ψp(ν)

causality + crossing subtracted dispersion rela=on:

Re Tψp(ν) = Tψp(0) + 2 π ν2 Z 1

νel

dν0 1 ν0 Im Tψp(ν0) ν0 2 − ν2

σtot

ψp = σel ψp + σinel ψp

σel

ψp ∝ Cel

⇣ 1 − νel ν ⌘bel ✓ ν νel ◆ael σinel

ψp

∝ Cin ⇣ 1 − νin ν ⌘bin ✓ ν νin ◆ain

parameterizing cross sec=on: directly sensi=ve to aψp

• O. Gryniuk

32

forward J/ψ - p scattering (II)

HERA/ZEUS (1995) EMC (1982) Fermilab (1980) CERN/WA58 (1987) SLAC (1984) σ (γp ccX) (μb) 0.01 0.1 1 10 W (GeV) 10 100 HERA (2002) Fermilab (1981) EMC (1980) SLAC (1975) Tψp(0) = 45 Tψp(0) = 22.45 Tψp(0) = 0 dσ/dt (t=0) (nb/GeV2) 1 10 100 W (GeV) 10 100

simultaneously fitting Vector meson dominance (VMD) assump=on:

σel

ψp =

✓Mψ efψ ◆2 ✓ qγp qψp ◆2 σ(γp → ψp) σinel

ψp

= ✓Mψ efψ ◆2 ✓ qγp qψp ◆2 σ(γp → c¯ cX) dσ dt

• t=0

(γp → ψp) = ✓efψ Mψ ◆2 ✓qψp qγp ◆2 dσ dt

• t=0

(ψp → ψp)

forward differential cross section:

Bψ ∼ 3 MeV

aψp ∼ 0.05 fm

Barger, Phillips (1975) Redlich, Satz, Zinovjev (2000) Gryniuk, Vdh (2016)

HERA (2002) Fermilab/E401 (1981) Fermilab/E516 (1983) Fermilab/E687 (1993) SLAC (1975) Cornell (1975) σ (γp J/ψ p) (nb) 0,1 1 10 100 W (GeV) 10 100

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Thanks for your attention and participation !