kent paschke

Kent Paschke

International Workshop on Neutrino Factories, Super Beams and Beta

BeamsJuly 25, 2012

Strangeness Content of the Nucleon

Kent Paschke

NuFACT, Williamsburg, Virginia, July 25, 2012

“Static” Strange Quarks in the Nucleon

Strange quarks exist in the nucleon at short distance scales.

Momentum ~ 4%

Magnetic moment, charge radiusMass 0-30% ,

Spin 0 - -10%

Strange contributions to nucleon matrix elements

are unsettled

Kent Paschke


Strangeness Nucleon Sigma Term The spin-independent neutralino-nucleon

scattering cross section as a function of ΣπN.Strange quarks coupling to the Higgs is much higher than that of the u/d flavors.The spin independent neutralino-

nucleon coupling varies by an order of magnitude depending on the strange condensate of the nucleon

Ellis et al, Phys.Rev. D77 (2008) 065026, arXiv:0801.3656

Dark Matter Searches

= 36 ± 7 MeV

Analyses of experimental data (πN scattering) implied large values of ΣπN ~ 65 MeV-> Large but uncertain σs ~ 350 MeV

σ0 estimated from known SU(3) breaking in the baryon octet: 36 ± 7 MeV

R.D. Young and A.W. Thomas, Nuclear Physics A 844 (2010) 266c

Recent lattice results claim high precision with small values for strange

quark mass contribution 15-60 MeV

Kent Paschke


Other Open Questions in Nucleonic Strangeness

NuTeV published a 3σ deviation from the standard model A leading hypothesis is that a signficant fraction is explained by an asymmetry in the strange sea:

NuTeV Anomaly

The spin dependent neutralino-nucleon coupling depends on Δs

Strange SpinOriginally motivated by the “spin problem”, but remains an important question in nucleon structure

Do the strange quarks in the sea play a significant role in the

electric/magnetic charge distributions in the nucleon?

?

Kent Paschke


Extracting the Strange Vector Form Factor

Two equations and three unknowns

Measuring all three enables separation of up, down and strange contributions

Measure neutral weak proton vector form-factor

Three equations and three unknowns

The weak form factor is accessible via parity violation

Charge Symmetry

Kent Paschke


Strange Form Factors in PVeSγ Z0

γ 2

€

~10−4Q2

GeV2

GsE only!

Spin=0,T=0 (4He):nuclear corrections: forward angle, low Q2 only

Deuterium:Enhanced GA

Back-angle quasi-elastic.

~ few parts per million

Forward angle Backward angle “Anapole” radiative corrections are

problematic

Proton:

p

Asymmetry of longitudinal polarized electron beam from unpolarized target

Kent Paschke


The Axial Term and the Anapole Moment

Axial form-factors GAp, GA

n

• Determined at Q2=0 from neutron and hyperon decay parameters (isospin and SU(3) symmetries)

• Q2 dependence often assumed to be dipole form, fit to ν DIS and π electroproduction

• Includes also Δs, fit from ν-DIS data (with significant uncertainties)

€

˜ G Ap,n = −τ 3 1+ RA

T = 1( )GA

( 3)

+ 3RAT = 0GA

( 8) + Δs

Anapole Moment Correction: Multiquark weak interaction in RA

(T=1), RA

(T=0) Zhu, Puglia, Holstein, Ramsey-Musolf, Phys. Rev. D 62, 033008•Model dependent calculation, with large uncertainty (~30% Model dependent calculation, with large uncertainty (~30% on axial FF)on axial FF)

•Dominates Uncertainty in Axial TermDominates Uncertainty in Axial TermDifficult to achieve tight experimental constraint Difficult to achieve tight experimental constraint Reduced in importance for forward-angle measurementsReduced in importance for forward-angle measurements

Kent Paschke


Axial Strange Form-FactorStrange axial form-factor related to integral over spin-dependent strange PDFs via QCD sum rule

Extrapolation of measurements of spin dependent structure functions are ambiguous:

Phys. Rev. D75 012007 (2007)

= −0.085 ± 0.013(th) ± 0.008(exp) ± 0.009(evol) HERMES (inclusive)

= 0.028 ± 0.033(stat) ± 0.009(ev) HERMES (semi-inclusive)

COMPASS (semi-inclusive)~ -0.01 ± 0.012 (exp)

DSSV helicity PDF fit reflects the HERMES SIDIS dominance: positive above x~0.05, with inclusive data dominating at lower xde Florian, Sassot, Stratmann and Vogelsang, Phys. Rev. D80 034030

(2009)

Kent Paschke


Neutrino NC elastic measurements for GA

s

G. Garvey et al., Phys. Rev. C48, 761 (1993).

= −0.21 ± 0.10 (exp) ± 0.10 (FF)

Fitting cross-section data from NC scattering in E734

L. A. Ahrens et al., Phys. Rev. D35, 785 (1987).

Very sensitive to Q2 dependence (axial mass MA)

Limited precision and moderately high Q2 reduce precision of bound on

Finesse Would have provided a precise, low Q2 measurement using a ratio of NC and CC quasi-elastic cross-sections, projected

In any case, this is a small contributor to the axial uncertainty due to radiative corrections for the vector strange FF measurements

Kent Paschke


Lead - Lucite Cerenkov Shower Calorimeter•phototube current integrated over fixed time periods

Hall A Parity: Integrating in the High Resolution Spectrometers

parts per million

Psuedo-random, rapid helicity flip

Very clean separation ofelastic events by HRS optics

no PID needed; detector sees only elastic events

Elastic

Inelastic

detector

Q Q

Dipole

Quad

target

Techniques for high flux, to get few percent precision on 1-20 parts per million asymmetry

Kent Paschke


Experimental Overview

SAMPLE

HAPPEX Precision spectrometer, integrating

A4

open geometry, integrating, back-angle only

Open geometry

Fast counting calorimeter for background rejection

Forward and Backward angles

G0

Open geometry

Fast counting with magnetic spectrometer + TOF for background rejection

Forward and Backward angles over a range of Q2

Forward angle, also 4He at low Q2

Kent Paschke


Forward-angle proton scattering

• ANS error: precision of EMFF (including 2γ), Anapole correction, and γZ box diagrams• Using experimental determination for axial form factor would increase total Ans uncertainty about 50%• Additional data at backward angles, and 2H and 4He target

Combining results from forward-angle proton scattering (similar beam energies):

“No net vector strangeness” line

Significant background challenges in G0 measurement

Kent Paschke


World Data at Q2 ~0.1 GeV2

Caution: the combined fit is approximate. Correlated errors and assumptions not taken into account.

For somewhat more careful treatment, see published fits by:R. Gonzalez-Jimenez, J.A. Caballero, T.W. Donnelly, arXiv:1111.6918orR. Young et al., Phys. Rev. Lett 97, 102002 (2006) orJ.Liu et al., Phys. Rev. C 76, 025202 (2007)

~3% +/- 2% of proton magnetic moment

~0.2 +/- 0.5% of Electric FF

95%

http://inspirehep.net/author/Gonzalez-Jimenez%2C%20R.?recid=1079260&ln=en

http://inspirehep.net/author/Caballero%2C%20J.A.?recid=1079260&ln=en

Kent Paschke


World data on Gs

all forward-angle proton data

At Q2 ~ 0.1 GeV2, Gs < few percent of Gp

Q2 ~ 0.22 Q2 ~ 0.62

Leading Order Fit

Kent Paschke


Simple fit

Fit includes only data Q2 < 0.65 GeV2 G0 Global error allowed to float with unit constraint

Simple fit:

GEs = ρs*τ

GMs = μs

• Simple fit (including all data, even if not shown)• Parameterization doesn’t matter... just “no bumps” • Data consistency is good (~20% confidence level)• Slight positive preference but low statistical significance• Contributions smaller than few percent of proton electric/magnetic form factors

Kent Paschke


Parameterizations

Fit includes all world data Q2 < 0.65 GeV2 G0 Global error allowed to float with unit

constraint

GEs = ρs*τ

GMs = μs

GEs = ρs*galster

GMs = μs*dipole

GEs = ρs* τ + a2*τ2

GMs = μs + m2*τ

Models would need “bumps” to find significant strange effects

Kent Paschke


Considering only the 4 HAPPEX measurements

• High precision• Small systematic error• ε>0.95 - relatively clean theoretical interpretation

Kent Paschke


Model guidance is unclear: kaon loops, vector dominance, Skyrme model, chiral quark model, dispersion relations, NJL model, quark-meson coupling model, chiral bag model, HBChPT, chiral hyperbag, QCD equalities, …

- Dong, Liu, Williams PRD 58(1998)074504 - Lewis, Wilcox, Woloshyn PRD 67(2003)013003 - Leinweber, et al.,PRL 94(2005) 212001; 97 (2006) 022001- Lin, arXiv:0707:3844- Wang et al, Phys.Rev. C79 (2009) 065202- Doi et al., Phys.Rev. D80 (2009) 094503

QCD models

Recent significant progress in Lattice QCD:

these all suggest very small effects with precision an order of magnitude beyond empirical constraints - predictions are

experimentally indistinguishable from zero

Kent Paschke


The Axial Term and the Anapole MomentAnapole Moment

Correction: Multiquark weak interaction in RA

(T=1), RA(T=0)

Difficult to improve on theoretical bound€

˜ G Ap,n = −τ 3 1 + RA

T = 1( )GA

( 3)

+ 3RAT = 0GA

( 8) + Δs

Uncertain Q2 dependence

G0 results

Young et al., Phys.Rev.Lett. 97 (2006) 102002, nucl-ex/0604010

Worse, if you assume that the correction might independently affect GA

p and GAn

G0 Collaboration, Phys.Rev.Lett. 104 (2010) 012001

Zhu

Leinweber

Zhu

(preliminary)

Kent Paschke


Proton Weak Charge

Proton weak charge precisely known from EW gauge theory and precision EW at the Z-pole

If measurement at low energy comes up different, indicates proton charged for some other (parity-violating) interaction

slope due to proton structure

Global fit of existing strange-quark program data provides constraint on Standard Model

Kent Paschke


Bounding the vector weak charge

SM value

R. Young et al., PRL 99 122003 R. Young et al., PRL 99 122003 (2007)(2007)

With this parameterization for hadronic effects, what can be said about the Standard Model parameters?

QpW = 2 C1u + C1d

These “form factor” measurements offer a

powerful constraint on new physics

Neutral weak charge of Up, Down quarks

Kent Paschke


Proton Weak Charge with QWeak

δQWp=4%

- Non-perturbative theoryNon-perturbative theory g g ~~ 2 2ππ ΛΛ ~~ 29 TeV 29 TeV

- Extra Extra Z’Z’ g ~ 0.45 g ~ 0.45 Z’Z’ ~~ 2.1 2.1 TeVTeV

Figure: R.Young

Dedicated proton form-factor at very low Q2: proton weak charge to 4%

Run concluded this May. Analysis underway. First results at October DNP!

Kent Paschke

LNS Colloquium, September 2011

Precision Electroweak Physics with e- beam

Steady progress in technology:

• part per billion systematic control

• 1% systematic control

• Major developments in

- photocathodes ( I & P )- polarimetry- high power cryotargets- nanometer beam stability- precision beam diagnostics- low noise electronics- radiation hard detectors

• pioneering• recent• next generation• futurePioneeringStrange Quark Studies3rd GenerationFuture Future:

•Qweak-electron (MOLLER at JLab)•Quark axial charges + nuclear studies (SOLID at JLab)•super Qweak-proton (P2 at Mainz)

SOLID: significant interplay with ν studies

Kent Paschke


Vector Strange Form Factors are Small

Q2 ~ 0.1

Q2 ~ 0.22

Q2 ~ 0.62

• Global results are consistent with strangeness contributions less than a few percent of the electromagnetic structure of the nucleon

• Recent lattice results indicate values smaller than these uncertainties

• Further improvements in precision on strange form factors would require additional theoretical (radiative corrections) and empirical (vector FF) input for interpretationVector strange quark program is winding down...

...nuclear and fundamental interaction studies with parity-violating electron scattering

continue

Kent Paschke


Kent Paschke


Backup

Kent Paschke


γZ box contributions

Tjon, Blunden, Melnitchouk (2009)

Also results from Zhou, Kao, Yang, Nagata (2010)

~10-3 for APV

Q2 dependent, but incomplete resonant states

1%-few% for APV

Sibirtsev, Blunden, Melnitchouk, Thomas (2010)

Also results from: Rislow, Carlson (2010),Gorchtein, Horowitz, M. Ramsey-Musolf(2011)

Complete calculations, but only at Q2 =0

Recent interest in radiative corrections which remain significant at low Q2

Current status: few% uncertainty over measurement range, from 20-50% of Ans error. Precision will be

improved.

Kent Paschke


SAMPLEBates Laboratory, 1998-2001Backward angle, H and 2H Q.E. at low Q2

Mirrors focus Cerenkov light from backscattered particles into shielded PMTs

Analog integration of PMT during beam burst

No magnetic or T.o.F. spectrometer; background is not excluded

Background Dilution:Non-light background 15-30%Non-Cerenkov background 10-15%Pion decay background 5-10%

Measured in specialized runs

GEANT simulation

Kent Paschke


PVA4 at MainzCalorimeter:1022 PbF2 crystals

10 cm LH2 target

20 A, 80% polarized beam

LuMo

MAMI Microtron, 2000-presentForward and backward angles, Hydrogen, D2 Q2 = 0.6, 0.23, 0.1 GeV2

1022 PbF2 calorimeter crystals distinguish elastic via energy resolution

Specialized fast counting electronics self-trigger and histogram energy distributions in overlapping 3x3 modules

Elastic rate: 10 MHz, total rate 100 MHz

Scintillator paddles in coincidence to tag charge in backangle studies

Kent Paschke


G0JLab, 2004 Forward angle H

Duty factor of 499 MHz CEBAF beam reduced to 31 MHz

Recoil protons detected in scintillators, segmentation defines Q2 point

T.o.F through toroidal spectrometer,Time histogram from specialized electronics

Simultaneous Q2 = [0.16,1] GeV2

pions,background elastic protons

inelastic protonslead collimators

elastic protons

detectors

targetbeam

Kent Paschke


G0 Backward Angle

Electron detectionTurn magnet/detector package aroundAdd Cryostat Exit Detectors (“CEDs”) to define electron trajectoryAdd aerogel Cerenkovs to reject pions

JLab, 2006

Back angle H, D2

One Q2 point for each beam energy

“tracking+PID” from magnetic spectrometer

Kent Paschke


Combining with PVeS

S. Pate et al., Phys.Rev. C78 (2008) 015207

Subtracting off the CC axial term

Simultaneous fit E734 with PVeS to control vector strange form factor contributions

How well is Q2 dependence known? (recent Miniboone and K2K results raise questions)

Robust over models of Q2 dependence?Anapole corrections to PVeS?

kent paschke

Documents

strange axial formfactor

strange sea

strange contributions

strange condensate

gaskent paschkenufact

pveskent paschkenufact

nucleonkent paschkenufact

nucleonstatic strange