Alfredo Vega

31 Pages·2016·0.86 MB·English

Nonperturbative strange sea in proton using wave functions
inspired by light front holography
Alfredo Vega
In collaboration with
I. Schmidt, T. Gutsche and V.
Lyubovitskij
LC2016,Lisboa,Portugal
September 5, 2016
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Outline
Introduction
Brodsky - Ma Model
Holographic Light Front Wave Functions
(s −s¯) Asymmetry with Holographic LFWFs
Final Comments and Conclusions
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Introduction
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Introduction
In many cases it is necessary to consider contribution of sea quarks and
gluons in order to understand hadron properties
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Introduction
Sea quarks in nucleon arise through 2 different mechanism:
• Nonperturbative (Intrinsic).
• Perturbative (Extrinsic).
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Introduction
(cid:63) Extrinsic sources of sea quarks. 1
• Arises from gluon radiation to qq¯ pairs.
• Include QCD evolution.
• Strongly peaked at low x.
• Extrinsic sea quarks require q = q¯. Asymmetries (very small, low x)
arise at NNLO order.
1
S.Catani,D.deFlorian,G.RodrigoandW.Vogelsang,Phys.Rev.Lett.93,152003(2004).
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Introduction
(cid:63) Intrinsic sources of sea quarks 2
• Arises from 4q+q¯ fluctuations of N Fock state.
• Atstartingscale,peakedatintermediatex; more”valence-like”than
extrinsic.
• In general, q (cid:54)= q¯ for intrinsic sea.
• Intrinsic parton distriutions move to lower x under QCD evolution.
2
e.gseeF.G.CaoandA.I.Signal,Phys.Rev.D60,074021(1999).
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3
Brodsky - Ma Model
3
S.J.BrodskyandB.Q.Ma,Phys.Lett.B381,317(1996).
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Brodsky-MaModel
Inthelight-frontformalismtheprotonstatecanbeexpandedinaseries
of components as
(cid:80)
|P(cid:105)=|uud(cid:105)ψ +|uudg(cid:105)ψ + |uudqq¯(cid:105)ψ +...
uud/p uudg/p qq¯ uudqq¯/p
• It is possible to consider a different light front approach, in which
thenucleonhascomponentsarisingfrommeson-baryonfluctuations,
while these hadronic components are composite systems of quarks.
• In this case the nonperturbative contributions to the s(x) and s¯(x)
distributions in the proton can be expressed as convolutions
(cid:18) (cid:19) (cid:18) (cid:19)
s(x)=(cid:82)1 dyf (y)q x and s¯(x)=(cid:82)1 dyf (y)q x
x y Λ/KΛ s/Λ y x y K/KΛ s¯/K y
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Brodsky-MaModel
(cid:18) (cid:19) (cid:18) (cid:19)
s(x)=(cid:82)1 dyf (y)q x and s¯(x)=(cid:82)1 dyf (y)q x
x y Λ/KΛ s/Λ y x y K/KΛ s¯/K y
• q and q are distributions of s quarks and s¯antiquarks in the
s/Λ s¯/K
Λ0 and K+, respectively.
• The functions f (y) and f (y) describe the probability to
Λ/KΛ K/KΛ
find a Λ or a K with light-front momentum fraction y in the KΛ
state.
• To do calculations we need wave functions.
f (y)=(cid:82) d2k |ψ (y,k)|2
B/BM 16π3 BM
q (x)=(cid:82) d2k |ψ (x,k)|2 and q (x)=(cid:82) d2k |ψ (x,k)|2
s/Λ 16π3 Λ s¯/K 16π3 K
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