[Cuga] 2nd Workshop on The Proton Mass; At the Heart of Most Visible Matter- a message from Zein-Eddine Meziani

[Lorelei Chopard]

Dear Colleague,


  We are happy to announce the 2nd workshop on the “Proton Mass; At the
  Heart of Most Visible Matter”. If you are interested in the workshop
  scientific program and believe you can contribute to one of the
  scientific questions please contact the organizers. Due to the limited
  space at the ECT* attendance is by invitation only.

*Circular:*

2nd Workshop on The Proton Mass; At the Heart of Most Visible Matter
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*Venue: ECT*, Trento, Italy*
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*Date: April 3-7, 2017*

*Motivation:*

The subject of understanding the proton mass in terms of its 
constituents, as naive as it may sound, is of paramount importance to 
the field of Hadronic/Nuclear physics. The emergence of hadron masses 
from quarks and gluons is one of the most fascinating subjects in 
coherence physics and a cornerstone of QCD. In a tour de force, 
calculations of the baryon mass spectrum in lattice QCD has been 
successfully carried out, however developing the intuition of  how the 
mass of each hadron emerges finds many pathways as noticed in the 
workshop held at Temple University in March of 2016 
(https://phys.cst.temple.edu/~meziani/proton-mass-workshop-2016/ 
<https://phys.cst.temple.edu/%7Emeziani/proton-mass-workshop-2016/>). 
How the mass of the proton emerges from its constituents is a natural 
and familiar question shared by many colleagues from other areas of 
physics where the mass of key systems is commonly described in terms of 
the mass of their constituents. While the mass of a hadron in QCD is an 
emergent phenomenon it is nevertheless important to cast our answer in 
terms of the energy/mass of the constituents in order to facilitate 
communication with the public in a familiar way. This is now crucial as 
the nuclear physics community in the U.S. and elsewhere embarks in the 
justification of building ever larger experimental facilities in the 
quest of understanding QCD and the structure of hadronic/nuclear matter 
from basic principles. In the U.S. such a facility is the electron ion 
collider (EIC) project which has been endorsed by the US nuclear physics 
community as the next construction project after the completion of FRIB. 
The science justification of this project will soon undergo an 
evaluation by a committee from the US National Academy of Science to 
cement its /raison d'être/. The quality and importance of the problems 
addressed by nuclear physics, especially those involving a true 
understanding of the inner workings of QCD need to identify connections 
and pathways to others areas of physics. The ``mass of the proton" is 
one theme amenable to emphasize what remains to be understood in QCD as 
a worthwhile goal that can be appreciated by the wider physics community 
not just the practitioners of hadronic/nuclear physics.

*Scientific Program:*

The workshopwill support a three-pronged theoretical approach to the 
subject of the origin of hadron masses with an added value on defining 
possible measurements that would make whole the investigation of the 
origin of the proton mass. This theoretical approach combined with 
experimental measurements should in principle allow for a deeper 
understanding of this complex subject. Direct lattice QCD calculations 
of hadron masses, mass decompositions, where the role of the 
constituents are explored, as well as phenomenological and approximated 
analytical approaches would form the three legs supporting the theory 
base of this workshop. Experiments  aimed at some specific pieces of 
this puzzle, for example the individual terms in a decomposition of the 
mass in terms of the constituents, could form a platform for 
experimental measurements that will be pursued if at all possible.

1-How can lattice QCD help us explore the role of "individual" 
constituents in making up the hadron masses? For example we want to 
explore the role of quark masses, in particular strange and heavy quark 
masses contribute to the proton mass.

2- What can the decomposition in terms of constituents teach us?  Can we 
take advantage of the non-uniqueness of the decomposition to cast it in 
terms of intuitive physical  and independently measurable quantities?

3- In the approximated analytical, phenomenological or model approaches, 
how well can we control  the approximations? Examples are the proton 
wave function, or the piN sigma term, how to quantify or improve the 
approximations made and how do different approaches compare with each 
other?

4- Identify new measurements that could be pursued at existing or future 
facilities and which would measure relevant observables closely linked 
to a given decomposition and could effectively test our assumptions. For 
example, measurements of the J/\psi electro- and photo-production at 
threshold at Jefferson Lab and the measurement of upsilon electro- and 
photo-production at threshold at a future Electron Ion Collider

*Websites:*

ECT* workshop webpage: http://www.ectstar.eu/node/2218

Scientific website: https://www.jlab.org/indico/event/194/

*Registration:*

The official administrative registration will be open on the ECT* 
webpage: http://www.ectstar.eu/node/2218
  startingJanuary 30, 2017 to  March 19, 2017.

*Organizers:*
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Zein-Eddine Meziani( Temple Univ.)
Barbara Pasquini (Univ. of Pavia)
Jianwei Qiu (Jefferson Lab)
Marc Vanderhaeghen (Univ. of Mainz)



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