neutrino-nucleus scattering at high energies tus k. saito
DESCRIPTION
Neutrino-Nucleus scattering at high energies TUS K. Saito. 東海 研究会 5 『 レプトン原子核反応型模型の構築に向けて 』 1/17. DIS kinematics ― what can we see in DIS ? N eutrino scattering at high Q 2 Neutrino scattering at low Q 2 Summary. 0. Lepton reactions. atmospheric. (GeV 2 ). GeV 2. QE. - PowerPoint PPT PresentationTRANSCRIPT
Neutrino-Nucleus scattering at high energies
TUS K. Saito
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 1/17
DIS kinematics ― what can we see in DIS ? Neutrino scattering at high Q2 Neutrino scattering at low Q2
Summary
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 2/17
0. Lepton reactions
(GeV)
(GeV2)
2
1
DISRES
Regge region
GeV2
BFKL evolution
DGLAP evolution
QE
atmospheric
T2K
1. Kinematics of Deep Inelastic Scattering (DIS) Initial and final lepton 4-momentum:
Virtual photon or boson 4-momentum squared:
Initial nucleon (nucleus) 4-momentum:
Final hadronic 4-momenyum squared:
y variable (--> energy loss at T rest fr.):
Bjorken variable:
0,, 222 mkkkk
0)( 222 Qkkq
22),,( TT MppEp
222 )( Wqpp f
EEkpqpy
1)/()(
12/0 2 TMQx
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 3/17
High momentum flow
High Q2: high resolutionPartons in target
W, Z,
p
pf
2. Charged current differential cross section:
lepton tensor current:
hadronic tensor (including anti-symmetric part):
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 4/17
V - A
Non-conservation of axial current
Non-conservation of parity
𝜈
ℓ−
𝑊+¿¿
left-handed
Cabibbo angle
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 5/17
The structure functions: 3 , because
: VV + AA contributions, : VA contributions.
difference between weak and EM interactions
Virtual boson helicity cross sections:
Def: , where
, where ,
average over T-polarizations
the right-left asymmetry
Note;
T: transverse
L: longitudinal
γ=|𝑞|𝑞0
𝐹 1=𝑀𝑁𝑊 1∝𝑊+1+𝑊 −1∝𝐹 𝑇
𝐹 2=𝜈𝑊 2∝𝑊 +1+𝑊− 1+2𝑊 0 ,𝐹𝐿=2𝑥𝑊 0
𝐹 3=𝜈𝑊 3∝𝑊+1−𝑊 −1
𝑒 ∙𝑞=0
3. Neutral-current differential cross section: 3
where
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 6/17
NC
4. What can we see in the target in the Bjorken limit
Bjorken limit The approximate Q^2-independence of the structure functions → the virtual photon sees point-like constituents in the target – quarks → using distributions of quarks and anti-quarks,
(Callan-Gross relation)
The small scaling violation is calculated by pQCD.
DIS probes a current-current correlation in the target ground state. In the Bjorken limit, the probed correlation is light-like:
~ 2.0(fm) for x ~ 0.1 ~ 1.0(fm) for x ~ 0.2 ~ 0.4(fm) for x ~ 0.5 ~ 0.2(fm) for x ~ 1.0
f
fff xqxqexF )],()([21)( 2
1
,2/)( 3yty xMyyy T/2,0,0
cxfmyt /)(2.0|||,| 3
)(2)( 12 xxFxF
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 7/17
)(),( 2,1:,,2
2,1
2
xFQxF fixedxQ
5. Simple consideration on the ν / ν reactions
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 8/17
The cross section may naively be given in terms of the incoherent sum of ν/ν-bar scattering off a quark:
1. neutrino-quark scattering (CC)
Then, average over the quark probability distribution q(x’) in a target,
2. neutrino-anti-quark scattering (CC)
𝜈
ℓ−
𝑊+¿¿
𝑝1=𝑥𝑝
𝑝2=𝑥𝑝+𝑞
3. Scattering-angle (or y-variable) dependence
4. Mixing-angle dependence
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 9/17
d’ term s’ term
h=-1/2
h=+1/2h=-1/2
5. Results (Leading order)
Average
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 10/17
𝜈𝑁
𝜈𝑁
isospin singlet (u d)
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 11/17
6. Parameterization of Nuclear PDF by HKN
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 12/17
7. Neutrino reactions at low Q2
(GeV)
(GeV2)
2
1
DISRES
?
GeV2
1. Kulagin prescription
only for low momentum transfer• the transverse cross section finite as Q2 0 (photo-absorption); FT 0 shadowing, VMD model, etc.
• the longitudinal cross section contains the VV and AA parts. the vector-current part FL
VC 0, because of the CVC; . only the axial-current part remains, because of the PCAC;
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 13/17
Separate the axial current as
(= pion current + heavy hadron current -- axial vector meson, ρπ continuum, etc.)
But, the pion derivative does not contribute, because
Thus,
(interference main term between jπ and A’)
πN (or A) scattering
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 14/17
Adding the form factor to cut off the large-Q2 contribution, we finally obtain
The πN forward scattering amplitude (the total cross section) is given by the Regge parameterization:
𝜋
𝐴𝑥𝑖𝑎𝑙𝑚𝑒𝑠𝑜𝑛
𝑁
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 15/17
shad
owin
g
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 16/17
2. A la Bodek and Yang
Their parameterization (for N) is very messy:
i = valence – up, down sea – up, down, strange j = sea – up, down, starnge
(for all Q2)
2
2
• At large Q2, we can see the quark-gluon structure of a target – pQCD + higher order corrections.
-- relatively easy to handle the structure functions (the quark-gluon distributions) even for a nucleus.• At low Q2, we need non-perturbative treatment: -- the Regge, the BFKL, BK and/or CGC approach, -- need a careful treatment on the axial current, -- nuclear (shadowing) effects.• How do we connect the two pictures ? • How do we connect to the resonance region ?
8. Summary
東海研究会 5『レプトン原子核反応型模型の構築に向けて』 17/17
F2A/F2
D
Slope of the EMC ratio
SLAC
3-1. Effect of the conventional nuclear physics ― Binding and Fermi motion
How does the conventional nuclear physics affect F2(x) ?
The nucleon is scattered incoherently in case of
The light-cone momentum distribution of N in A:
Spectral function Quasi-elastic reaction A(e,e’p)A’ → Koltun sum rule: E/A = (T-e)/2 (2body force only)
3. Theoretical approaches
1.02 xfmdc
22
4
42
/),( )()2(
),( ppMM
qPqpypSpdypyD A
AjAnpj
3-1. Effect of the conventional nuclear physics ― Binding and Fermi motion3-2. Shadowing effect at small x3-3. Anti-shadowing ?
APpy /
ApApS |)0(ˆ|,)1()(
2
0 |)(|)(2 pTMp R
p
Convolution form:
Assumptions in the convolution model: on-mass shell approximation → → if the binding is weak, OK? impulse approximation ― final state interactions and interference terms are ignored.
If OK, we get
Model-dependent calculations:① Off-mass shell effect by Kulagin et al. ↓② Off-mass shell (↓) + final state interaction (MFA) by Saito et al. ↑
Ignored diagrams
Note: Deuteron is also different from the average of proton and neutron ― small EMC effect.
22 Mp
),(),()()( 2/
2
,/
2/ pzfpyDdpyzxdydzxf ja
jAjAa
,2/2 )/()()(
j
jAj
A
x
A yxFyDdyxF
Nonrelativistic calculation (by Li, Liu, Brown)
(by Atti, Liuti)
Relativistic calculation (by Smith, Miller)
What is missing ?Final state interaction:
q 2 pQCD (OPE) k di-quark (light-cone exp.)
p MF
A-1
A
K. Saito, A.W.T., N.P.A574, 659 (1994).
No fermi motion, no c.m. correction
Quark picture, but no FSI
Quark picture with FSI
Naïve Bag model calculation – include not only FSI but also SRC
SLAC-E139Fe & Ag
Drell-Yan exp.
FNAL-E772W
Chiral Quark Soliton model calculation
R.S.Jason, G.A. Miller, P.R.L.91, 212301 (2003).
NJL model calculation
I.C. Cloet, W. Bentz, A.W.T., Phys.Lett.B642, 210-217 (2006).
3-2. Shadowing effect at small x
Shadowing region →
DIS occurs coherently:
>> 1 for x > 0.1 << 1 for x < 0.1 for small x, the photon is supposed to be converted into vector mesons VMD → surface interaction
1.02 xfmdc
)()( 8.02 NANAA AAxF
ba AA /
8.03/2 AA
Shadowing effect (by Piller et al.)
NMC+FNAL ( ) ,,
3-3. Anti-shadowing ?
Anti-shadowing region →
An enhancement at small x region → pion field enhancement ???
Recent data of the giant Gamow-Teller states → the Landau-Migdal parameters
2.01.0 x
ggg NNN 05.018.0,59.0
4. Summary
1. The quark distribution in a nucleus is different from that in the free nucleon: ― about 20% reduction at x ~ 0.7-0.8 ― at small x, the structure function is reduced due to shadowing ― for large x, the EMC ratio is very enhanced because of Fermi motion and short-range correlation
2. The energy-momentum distribution of a nucleon in a nucleus is vital to explain the EMC effect, but its effect is insufficient ? ― the internal structure of a nucleon is modified in a nucleus ?
3. The sea quark is enhanced in a nucleus around x ~ 0.15 ? ― cf. the Drell-Yan result
4. At large x (>1), what happens ? new JLab data !
x
σx = Q^2/2Mν, Q^2 fixedν large, x smallvery low Q^2
A1
elastic
x
σvery low Q^2
A1
elastic + excited states
x
σlow Q^2
A1
QE peak displacement energy
x
σmid Q^2
A1
QEΔ
N*
x
σmid Q^2
A1
Δ, N* duality
QE peak of quark
1/3
x
σhigh Q^2
A1
valence quark
1/3
x
σvery high Q^2
A1
sea + glue BK region
1/3
Comment on the QE peak in e-A scattering
T. Suzuki, P.L.B101 (1981), 298R. Rosenfelder, P.L.B79 (1978), 15
QE peak in e-A scattering at low energyDifferential cross section:
The response functions (structure functions):
S = W(L) or W(T) for longitudinal mode
The characteristic function:
(k-th energy weighted moment)
The characteristic function is described in terms of the cumulants;
The displacement energy at the peak of QE cross section can be given by the cumulants; (0).
σ
ω
The 1st moment is then given by
If we take Hamiltonian as
,then we get (as an example, for longitudinal mode)
,which implies that the Wigner and Bartlett forces do not contribute to the displacement energy (for longitudinal mode) !
Summary: • the displacement of QE peak is caused by some specific forces in nuclear force.• the binding effect appears when FSI is ignored, while, if it is include, the binding is cancelled by FSI – Wigner force does not contribute. • the energy shift is also caused by a non-local (energy dependent) one-body potential.
By Atti and West
y scaling