A new twist in the spin puzzle of proton

A new twist has appeared in proton spin crisis.

1. u and d sea antiquarks contribute differently to proton spin which looks very strange if sea quarks originate from the decays of gluons as perturbative QCD predicts.
   
   
2. The amount of dbar type sea quark is larger than that of ubar type sea quark. But the amount of proton spin assignable to dbar quark is smaller!
   
   

In TGD framework these findings give very valuable hints concerning the detailed structure of proton and also the proper interpretation of what are called sea quarks.

First of all, the notion of sea parton is rather fuzzy statistical notion tailored to the needs of perturbative QCD. Could it be that there could be a much more structured description analogous to that of atom or nucleus? In TGD framework nuclear string model describes nuclei as collection of nucleons connected by flux tubes having quark and antiquark at ends.

What does one obtain if one applies this picture to the ealier model in which valence quark space-time sheets are assumed to be connected by color flux tubes having quark and antiquark at their end forming meson like states. Consider the following picture.

1. uud with standard wave function describes valence quarks which are almost point like entities assignable to partonic 2-surfaces.
   
   
2. There are 3 color bonds in the triangle like structure formed by valence quarks. Assign to these
   
   • dbar-d spin singlet analogous to pion with spin 0,
     
   • dbar-u spin singlet analogous to pion with spin 0 ,
     
   • ubar-d vector analogous to ρ meson with spin 1.
     
   Identify the quarks and antiquarks of color bonds with the TGD counterpart of the sea.
3. Bonds would carry total spin 1. As one forms spin 1/2 state with valence quarks with spin 1/2 valence quarks carry vanishing spin in the resulting state: this solves the core part of proton spin puzzle. Given valence quark has vanishing average spin due to the entanglement with bonds.
   
   
4. Also the observations can be understood qualitatively.
   
   • The amount dbar in the sea is two times larger than the amount of ubar.
     
   • The average contribution of dbar to spin is vanishing in spin singlet bonds and spin 1 bond does not even contain dbar. Hence the average contribution to sea quark spin vanishes.
     
   • The contribution of ubar in ubar-d spin 1 bond is non-vanishing and experimentally known to be larger than that dbar sea quark.
     

This model could also allow to understand how the old-fashioned Gell-Mann quark model with constituent quarks having masses of order m_p/3 about 310 MeV much larger than the current quark masses of u and d quark masses of order 10 MeV.

1. I have proposed that the current quark + color flux tube would correspond to constituent quark with the mass of color flux tube giving the dominating contribution in the case of u and quarks. If the sea quarks at the ends of the flux tubes are light as perturbative QCD suggests, the color magnetic energy of the flux tube would give the dominating contribution.
   
   
2. One can indeed understand why the Gell-Mann quark model predicts the masses of baryons so well using p-adic mass calculations. What is special in p-adic calculations it is mass squared, which is additive as essentially the eigenvalue of scaling generator of super-conformal algebra denoted by L₀.
   

   m²_p= ∑ m²_p,n
   

   This due to the fact that energy is replaced by mass squared, which is Lorentz invariant quantity and conformal charge. Mass squared contributions with different p-adic primes cannot be added and must be mapped to their real counterparts first. On the real side is masses rather than mass squared, which are additive.
   
   

3. Baryon mass receives contributions from valence quarks and from flux tubes. Flux tubes have same p-adic prime characterizing hadron but quarks have different p-adic prime so that the total flux tube contribution m²(tube)_p mapped by canonical identification to m_R(tubes)= (m²_R(tubes))^1/2 and analogous valence quark contributions to mass add up.
   

   m_B= m_R(tube)+
   ∑_q m_R(valence,q).
   

   The map m²_p→ m²_R is by canonical identification defined as
   

   x_p= ∑_nx_npⁿ→ x_R= ∑ x_np^-n
   

   mapping p-adic numbers in continuous manner to reals.
   
   

4. Valence quark contribution is very small for baryons containing only u and d quarks but for baryons containing strange quarks it is roughly 100 MeV per strange quark. If the dominating constant contribution from flux tubes adds with the contribution of valence quarks one obtains Gell-Mann formula.
   
   

A detailed estimate for nucleon mass using p-adic mass calculations shows the power of p-adic arithmetics even in the case that one cannot perform a complete calculation.

1. Flux tube contribution can be assumed to be independent of flux tube in the first approximation. Its scale is determined by the Mersenne prime M_k= 2^k-1, k=107, characterizing hadronic space-time sheets (flux tubes). Electron corresponds to Mersenne prime M₁₂₇ and the mass scales are therefore related by factor 2^(127-107)/2≈ 2¹⁰: scaling of electron mass m_e,127= .5 MeV gives mass m_e,107≈ .5 GeV, the mass electron had if it would correspond to hadronic p-adic length scale.
   

   p-Adic mass calculations give for the electron mass the expression
   

   m_e≈ [1/(k_e+X)^1/2] 2^-127/2m(CP₂) .
   

   k_e=5 corresponds to the lowest order contribution. X<1 corresponds to the higher order contributions.
   
   

2. By additivity of mass squared for flux tubes one has m²(tubes)= 3m²(tube,p) and m_R(tubes)=3^1/2m(tube,R): one has factor 3^1/2 rather than 3. Irrespective whether m_R(tubes) can be calculated from p-adic thermodynamics or not, it has general form m²(tube,p)= kp in the lowest order - higher orders are very small contribute to m²_R at most 1/p. k is a small integer so that even one cannot calculate the its precise value one has only few integers from which to choose.
   The real mass from flux tubes is given by
   

   m_R= (3k_p/M₁₀₇)^1/2× m(CP₂) =(3k_p/5)^1/2× m(e,107).
   

   For k_p= 6 (for electron one has k_e=5) one has m_R(tubes)= 949 MeV to be compared with proton mass m_p= 938 MeV. The prediction is too large by 1 per cent.
   
   

   
   

3. Besides being by 1 per cent too large the mass would leave no room for valence quark contributions, which are about 1 per cent too (see this). There error would be naturally due to the fact that the formula for electron mass is approximate since higher order contributions have been neglected. Taking tis into account means replacing k_e^1/2=5^1/2 with (5+X)^1/2, X<1, in the formula for m_R. This implies the replacement m_e,107→ (5/(5+X)^1/2m_e,107. The correct mass consistent with valence quark contribution is obtained for X=.2. The model would therefore fix also the precise value of m(CP₂) and CP₂ radius.
   
   

These observations give good hopes that this model replacing quark sea with color bonds solve the proton spin crisis.

What about the masses of Higgs and weak bosons?

p-Adic mass calculations give excellent predictions for the fermion masses but the situation for weak boson masses is less clear although it seems that the elementary fermion contribution to p-adic mass squared should be sum of mass squared for fermion and antifermion forming the building bricks of gauge bosons. For W the mass should be smaller as it indeed is since neutrino contribution to mass squared is expected to be smaller. Besides this there can be also flux tube contribution and a priori it is not clear which contribution dominates. Assume in the following that fermion contributions dominate over the flux tube contribution in the mass squared: this is the case if second order contributions are p-adically O(p²).

Just for fun one can ask how strong conclusions p-adic arithmetics allows to draw about W and Z masses m_W=80.4 GeV and m_Z= 91.2 GeV. The mass ratio m_W/m_Z allows group theoretical interpretation. The standard model mass formulas in terms of vacuum expectation v=246.22 GeV of Higgs read as m_Z= (g²+(g')²)^1/2v/2 and m_W= gv/2= cos(θ_w)m_Z, cos(θ_W)= g/(g²+(g')²)^1/2.

1. A natural guess is that Higgs expectation v=246.22 GeV corresponds to a fundamental mass scale. The simplest guess for v would be as electron mass k_e^1/2 m₁₂₇, k_e=5, in the p-adic scale M₈₉ assigned to weak bosons: this would give v= 2¹⁹× m_e≈ 262.1 GeV: the error is 6 per cent. For k_e=4 one would obtain v= 2¹⁹× (4/5)^1/2m_e≈ 234.5 GeV: the error is now 5 per cent.
   

   For k_e=1 the mass scale would correspond to the lower bound m_min=117.1 GeV considerably higher than Z mass. Higgs mass is consistent with this bound. k_h=1 is the only possible identification and the second order contribution to mass squared in m_h²∝ k_h+X_h must explain the discrepancy. This gives X_h= (m_h/m_min)²-1≈ .141,
   

   Higgs mass can be understood but gauge boson masses are a real problem. Could the integer characterizing the p-adic prime of W and Z be smaller than k=89 just as k(π)=111=k(p)-4 is smaller than kp?
   
   

2. Could one understand cos(θ_w) = m_W/m_Z≈ .8923 as a ratio (k_W/k_Z)^1/2 obtained using first orderp-adic mass formulas for m_W and m_Z characterizing the masses in the lowest order by integer k? For k_W=4 and k_Z=5 one would obtain cos(θ_W)= (k_W/k_Z^1/2= .8944..: the error is .1 per cent. For k_Z=89 one would however have m_Z=v=m_e,89, which is quite too high. k=86 would give m_Z= 92.7 GeV: the error is 1.6 per cent. For m_e∝ (5+X_e)^1/2, X_e≈ .2 deduced from proton mass, the mass is scaled down by (5/(5+X_e)^1/2 giving 90.0 GeV, which is smaller than 91.2 GeV: the mass is two large by 2 per cent. Higher order corrections via X_Z=.05 give a correct mass.
   

   k=86 is however not consistent with the octave rule so that one must k_Z=k_W=85 with (k_W,k_Z)=(8,10). This strongly suggests that p-adic mass squared is sum of two identical contributions labelled by k_W=4 and k_Z=5: this is what one indeed expects from p-adic thermodynamics and the representation of gauge bosons as fermion-antifermion bound states. Recall that also for hadrons proton and baryonic space-time sheet correspond to M₁₀₇ and pion to k(π)=k(p)-4=111.
   
   

3. There can be also corrections characterized by different p-adic prime: electromagnetic binding energy between fermion and anti-fermion forming Z boson could be such a correction and would reduce Z mass and therefore increase Weinberg angle since W boson does not receive this correction. Higher order corrections to m_W and m_Z however replace the expression of Weinberg angle with cos(θ_W)= (k_W+X_W/(k_Z+X_Z)^1/2 and allow to obtain correct Weinberg angle. Note that canonical identification allows this if the second order correction is of form rp²/s, s small integer.
   
   

To sum up, it is fair to say that p-adic mass calculations allow now to understand both elementary particle masses and hadron masses. One cannot calculate everything but p-adic arithmetics with mild empirical constraints fix the masses with 1 per cent accuracy.

See the article Two anomalies of hadron physics from TGD perspective or the chapter New Physics predicted by TGD: Part I.

For a summary of earlier postings see Latest progress in TGD.

Articles and other material related to TGD.