Nucleon strangeness – present and future

EFB21, Salamanca1

M.G.Sapozhnikov Joint Institute for Nuclear Research, Dubna

Nucleon strangeness – extrinsic and intrinsic Scalar channel – contribution to the nucleon massMeasurements of Gs

E and GsM

s(x) = s(x) ??New measurements of s(x) (COMPASS)Future experiments – old problems

Strangeness of the nucleon

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S.Brodsky:

Extrinsic – connected with gluons – perturbativeq gluons s s gluons

Intrinsic – connected with valence quarks nonperturbative

|N > = |uud> + |uud s s> + …

What interaction connects (ss)- pair and valence quarks?

What are the quantum numbers of the s s – pair?How large is ?

Does it exist?

Strangeness of the nucleon: extrinsic

GRV98No strangeness

at 2 =0.3 GeV2

At large Q2 the QCD evolution creates ss admixture

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Intrinsic nucleon strangeness: possible signals

)]()()()([ xsxsxsxsdxs

Large contribution to the nucleon mass <N|ss |N>More s(x), than the extrinsic strangeness

predictss(x) s(x) |N> = |M N>, M , K, …. ; N= , N*, …

s –quark associated with a baryon

s – quark - with a meson

Non-zero polarization of strange sea

s(x) s(x)

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Strangeness – scalar channel

<N|ss |N>

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Strangeness of the vacuum

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The vacuum strange quark condensate is as large as the light quark condensate:

Ioffe B.L., Nucl.Phys. 1981, B188, 317, erratum 1981, B191, 591.

Reinders L.J., Rubinstein H.R., Phys.Lett., 1984, B145, 108.

B and Bs –mesons decay constants (lattice calculations, M.Jamin, Phys.Lett. B538 (2002) 71-76 )

0||0)1.08.0(0||0 qqss

0||0)3.08.0(0||0 uuss

<N|ss |N>

= N - CD - R

N =64 8 MeV, measured in N scattering (KH80)

= 45 MeV - calculated (ChPT, Gasser,Leutwyler)0 = (36 ± 7) MeV (Borasoy, Meissner, from baryon octet

mass splittings)

y= 0.210.20

pdduupM

m

p

||2

ˆ

)(2/1ˆ du mmm

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pddppuup

psspy

||||

||2

yy

pssdduupm

11

|2| 0

Strangeness of the nucleon

Old N data: y=0.20.2

“New” N data: y=0.36-0.48

(Meissner U.-G., Smith G., hep-ph/0011277)

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pddppuup

psspy

||||

||2

vity

J.Ellis, K.Olive, Ch.Savage Phys.Rev.D 77, 065026(2008) Important for the spin independent part of the elastic cross section of the supersymmetric particles:

Sensitivity of N to N

9 EFB21, Salamanca

Scalar channel <N|ss |N> J.Ellis, K.Olive, Ch.Savage Phys.Rev.D 77, 065026(2008)

“We plead for an experimental campaign to determine better the -π nucleon σ-term.”

“This quantity is not just an object of curiosity for those interested in the structure of the nucleon and non-perturbative strong-interaction effects: it may also be key to understanding new physics beyond the Standard Model.”

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Strangeness of the nucleon

Results of recent lattice calculations:

11

pddppuup

psspy

||||

||2

Latticey0.03

H.Ohki et al, hep-lat/0910.3271 Young,Thomas, hep-lat/0911.1757

Is the y large ?

May be not

Experimental situation - unclear

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Strangeness – vector channel

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How to measure the strange quarks contribution to electromagnetic formfactors?

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L (s p) =-1 R (s p) = +1 ALR = (L-R)/ (L+R)How ALR connects with strange quarks?

pepe

Neutral currents

J(NC)= uu + dd +ss + …

uu, dd – we know

cc, bb - omitted

One could calculate the contribution ofss

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e-

e-

e-

e-

p p

Z

iR

iR

iR

iL

iL

i

iL ggNCJ )(

D. Armstrong & K.Carter, CERN Courier 45, 8 (2005)

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Global fit analysis

J.Liu et al, PRC76 (2007) 025202

GEs = -0.008±0.016

GMs = 0.29±0.21

Impact of the Jlab dataLet us assume that, indeed:

Gs(E) ~ 0

Gs(M) > 0

Non-trivial consequences for ss – quantum numbers, 5q-admixture and s

)]()()()([ xsxsxsxsdxs EFB21, Salamanca18

If µs >0 and large…

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C.An, D.Riska, B.Zou, Phys.Rev.C73:035207,2006 From SAMPLE value:GM(s) = 0.37 0.20 0.26 0.07

s in S-state, uuds - in P-state Pss =| Ass |2 = 0.17 – 0.22

Pss ~ 0.19 – from analysis of the OZI violation in annihilation of low energy antiprotons J.Ellis et al, PL B353 (1995) 319

s = - 0.06 … -0.07 s = - 0.09 ± 0.01 ± 0.02 – COMPASS DIS

Recent measurements are not in favor of the s>0 variant

Strange vector form factorsA4 Coll. S.Baunack et al. Phys.Rev.Lett. 102,151803 (2009)GE

s = 0.0500.0380.019 GM

s = -0.0140.0110.011Lattice calculationsR.D.Young, nucl-th/1004.5163GM

s = -0.0460.022

Global data analysisR.D.Young et al. Phys.Rev.Lett. 99,122003(2007)GE

s = 0.0020.018

GMs = -0.010.25

20

Experimental uncertainties are still large

Are s and r2s 0?

It seems so…

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s(x) and s(x)

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Strangeness – least constrained distribution among the light quarks

Accurate determination of the strange sea is necessary for interpretation of the precise experimental data at LHC.

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CTEQ5L

GRV98LO

s(x) from different PDF analysis

Q2 = 4 GeV2

Experimental input for s(x)

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NuTeV: 5102 induced and 1458 CCFR : 5030 induced and 1060

D.Mason et al., PRL 99, 192001 (2007)

Determination of s(x) and s(x)

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•3 bins in neutrino energy•3 bins in z•5 bins in x

Separate determination of s(x) and s(x)

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)]()([ xsxsxdxS

S- =(1.960.460.45)10-3

• Maximum – at x0.05• Large statistical uncertainty• Large systematics

28

Bourrely C.,Soffer J.,Bucella F., PLB 648(2007)39Statistical parton modelModel parameters are from thefit of the CCFR and NuTeV data

S- = - 1.9410-3 s s < 0

Large x effect

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F-G Cao, A.Signal, PRD68(2003)074002Meson-baryon model

S- = - 1.9410-3 s < s s + s = +0.01K and K* - included

Large x effect

Perturbatively generated S-

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S.Catani et al, PRL93(2004)152003Perturbative evolution in QCD at three loopsInitial condition – S-=0

S- = -510-4

Small x effect

Is s(x) s(x) ?

UNCLEAR

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New data on s(x) and s(x)

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Inclusive DISEMC (1989)s + s = -0.18 0.05

HERMES (2009)s + s = -0.085 0.008(exp) 0.013(th) 0.009(evol)

COMPASS (2009)s + s = -0.09 0.01(exp) 0.02(syst)

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Nucleon strangeness from DISInclusive DISa3 = u - d = (F+D)(1+2) = 1.2690.003 –

from neutron -decaya8 = u + d -2 s =(3F-D)(1+3)

=0.586±0.031 – from hyperon decays

a0 = u + d + s 0.24 Assuming 2= 3 =0 u 0.81, d -0.46, s -0.12

36 EFB21, Salamanca

)]4(3

1[

12

1)( 08311 aaaxdxg

Flavour separation of the helicity quark distributions

37COMPASS Collaboration, Phys.Lett. B680 (2009) 217.

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LO helicity quark distributions

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SIDIS asymmetries for protonCOMPASS Collaboration, hep-exp/1007.4061.DSSV, Phys.Rev.D80 (2009) 034030

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no difference between s and s

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• No polarization of the sea quarks in the measured region• Good agreement with DSSV global fit

Is the nucleon strangeness polarized?S<0, but at small x

DSSV fit

41 EFB21, Salamanca

006.0057.0 s

11.0 ss

Are there any signals of intrinsic strangeness?

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Nucleon mass, scalar channel – not clearElectromagnetic form factors – nos(x) – s(x) - not clearPolarization of the strange quarks – not clear s = 0, DIS data analysis is not correct – no IS effects at

alls = -0.09, SIDIS data analysis is not correct (LO,

uncertainty in FF)s = -0.09, SIDIS data analysis is correct, polarization is at

small x – polarization is due to gluonsExtrinsic s(x) is too small - needs experimental

confirmation and spin transfer

Future experiments for strangeness

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COMPASSMore data on SIDIS FF determination and polarization

MiniBooNE, T2KN elastic scatteringPANDA, PAX at FAIR Strangeness production and spin transfer in

annihilation

production in DIS, quark fragmentation

45

Spin transfer from polarized quark

Quark fragmentation

Spin transfer from polarized muon

spin structure

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Spin transfer to

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(ud)I=0,S=0

S = Ss-quark

u d s

dus

spin structure

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SU(6) quark model: s = 1, u = d = 0100% polarization to u or d quarks is no influence on polarization of P() - 0 (for u –quarks dominance)

Burkardt-Jaffe: u = d = -0.23 P() – negative

B.Q.Ma et al.: u = d =s

P() – positive Lattice calculations: u = d ~0, s=0.68 P() ~ 0

Production of and is mainly due to fragmentation of target remnant () and u,d-quarks (,)

Spin transfer to and is mainly due to interaction with strange quark and antiquark

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N() N()

E665 750 650

NOMAD 8 087 649

HERMES 26 000 3 100

RHIC 12 000 10 000

COMPASS,03-04 70 000 42 000

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COMPASS,Eur.Phys.J. C64 (2009) 171.

Comparison of and : x

DLL() = -0.012 ± 0.047 ± 0.024

DLL() = 0.249 ± 0.056 ± 0.049

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DLL() DLL()

The results are averaged over target polarization

Preliminary

COMPASS,Eur.Phys.J. C64 (2009) 171.

Polarization of from quark fragmentation

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)()]()()([

)()]()()([2

2

zDxqyDPPxqe

zDxqPxqyDPeP

qTbqq

qTbqq

Spin transfer from polarized muon

Spin transfer from polarized quark

qqq DDD qqq DDD

52

CTEQ5L

GRV98, pure extrinsic

strangeness

DLL(s)=0, BJ model

DLL(s)=0, SU(6) model

Sensitivity to the strange distribution s(x)

Polarization of is the test of nucleon intrinsic strangeness existence

Determination of s in p elastic scattering

MiniBooNEs=0.080.26(hep-exp/

1007.4730)

T2K - ?53

E734, G.T.Garvey et al, PR C48 (1993) 761

s=-0.150.07

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J.Ellis, K.Olive, Ch.Savage

At LEAR experiments

Strong violation of the OZI rule was found in

pppp, pp (3S1)pdnDoes it depend on

spinorbital angular

momentummomentum transferisospin?

Spin transfer in p ppol +

PS 185 at LEARPolarized proton

targetDnn – spin transfer

from proton to Knn – spin transfer

from proton to

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Conclusions

No clean signatures of the intrinsic strangeness

Experimental information on s(x) – 45 data points

s – does it exist? May be an effect of gluons (axial anomaly)

New dedicated measurements are badly needed

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G0 collaboration, PRL 95 (2005)

092001

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without contribution

from s quarks,“disfavored with 89%

confidence”

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The is in the S-state, Not KΛ like!

B.S.Zou & DOR, PRL 95, 072001 (2005)

D.O.Riska,PANIC05

Probability of uuddss

component

s=-1/3 Pss

in both cases

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M.Wakamatsu, PRD67(2003)034005Chiral quark soliton model

Oscillating S- s >> s s < 0

PL: dependence on the target polarization

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P= P--P+ =-0.010.04, = 0.010.05,

Determination of the -term

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RqqttDF ')(),(2

To measure D +(t,) – isoscalar amplitude of N scattering

To extrapolate it at t=2m2 , =s-u=0 - CD=2

MeVTo extrapolate it at t=0, =0 - R = 15 MeV

N = + CD + R

= 64 ± 8 MeV – measured = 45 MeV - calculated

Nice agreement: 64 ± 8 = 45+2+15=62 MeV

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0 = 26…36 MeV

0 = (36 ± 7) MeV (Borasoy, Meissner, from

baryon octet masses)

= 45 MeVy=0.2 ± 0.2

pddppuup

psspy

||||

||2

yy

pssdduupm

11

|2| 0

pssdduupm |2|0

Quantum numbers of ss in nucleon

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|p> = |uud> + Ass |uud ss> + ….

P(p) = + , P(|uud ss) = - , if all q in S-state

(-1)L is needed

1) uuds in S-state, s - in P-state 2) s in S-state, uuds - in P-state

typical data ingredients of a global pdf fit

J.Stirling, DIS08 EFB21, Salamanca66

Sensitivity to the strange distribution s(x)

D.Naumov, Trento-08EFB21, Salamanca67

Strong dependence on the fragmentation functions

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dzzD

dzzDR

Ku

Kd

UF)(

)(

dzzD

dzzDR

Ku

Ks

SF)(

)(

RUF = 0.13 RSF =6.6 - DSS, Phys.Rev.D75(2007) 114010RUF = 0.35 RSF =3.4 - EMC, Nucl.Phys. B321 (1989) 541

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Large uncertainty on the strange quark fragmentation functions