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Fatiha Benmokhtarbenmokhtarf@duq.edu

Studies of Partonic

Distributions using Kaon SIDIS

Duquesne University, Pittsburgh, PA, USA

MENU 2019, Pittsburgh, PA

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Flavor decomposition Program using polarized and unpolarized Semi-

Inclusive hadron production from polarized and unpolarized hydrogen

and deuterium targets using CLAS12 detector enhanced with a RICH

counter

The Hybrid Ring Imaging Cerenkov Counter (RICH)

Expected Precisions and outlook

Outline

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Flavor Contributions to the Nucleon

Spin

Gq LΔGLΔq2

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2

1

q

S

sΔΔsdΔΔduΔΔuΔq ,,,,,

-Our interest is on getting all the flavors! With a special interest of the strangeness.

« sea= virtual pairs »valence

As you saw, this morning, from M.

Contalbrigo and R. Seidl talks.

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E12‐09‐007 CLAS12 – Jefferson Lab-CLAS12 (H. Avakian, F. Benmokhtar, A. EL Alaoui, K. Hafidi & M. Mirazita)

Goal: Measurements of pions and kaons multiplicities and longitudinal double spin asymmetries using SIDIS off hydrogen and deuterium targets. Extract all the flavors!

Control of the fragmentation functions used in the extraction of the individual quark and antiquark contribution to the nuclear spin.

shape of the strange pdfs.

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Flavor decomposition

Unpolarized Measurements Polarized Measurements

Proton Deuteron Deuteron Proton

E12‐09‐007 CLAS12 – Jefferson Lab (H. Avakian, F. Benmokhtar, A. EL Alaoui, K. Hafidi & M. Mirazita)

Extract shape of

x(s(x) s(x))

Extract

x(s s)

x(u u d d)

Extract

xu,xd,xs,xu,xd,xs,x(ud)

Isoscalar Method

Flavor Decomposition

Measure Multiplicities

(π+ + π-, K+ + K-, Ks0)

Measure Asymmetries

(e-, π+ + π-, K+ + K-, Ks0)

Measure Multiplicities

(π+, π-, π0, K+, K-, Ks0)

Measure Asymmetries

(e-, π+, π-, π0, K+, K-, Ks0)

*Extraction of Δu − Δd to

test whether or not the

light sea is symmetrically

polarized

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)Xepe( h

μν

μν'4

2

WLE

E

MQ

α

dEd

d

'

2

= E-E’

x = Q 2 /(2M )

y = /E

W 2 = M 2 - 2M - Q2

Q 2 = 4EE’sin 2(θ/2)

Semi Inclusive DIS

Hadron Selection: z = Eh /

xF = 2 |p||| / W

SIDIS Selection:

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Measurement of Δq in Semi-Inclusive DIS

Select PDFs : q -(x) or q +(x) by changing the orientation of target nucleon spin or helicity

of incident lepton beam

Leading order

Double spin asymmetry

xq

xq

zdzDxqe

zdzDxqe

qq

h

qq

h

qq

~2

2

zxPh

q , - Dqh is a measure of the probability that

a quark of flavor q will fragment into a

hadron of type h = fragmentation

function

- Pqh Purity is a conditional probability

that a hadron of type h observed in the final state is originated from a struck quark of flavor q in case of unpolarized beam/target.

A(x,Q2) (A1p,A1p

,A1p

,A1p 0 ,A1p

K

,A1pK

,A1pKs0

,A1d ,A1d

,A1d

,A1d 0 ,A1d

K

,A1dK

,A1dKs0

)

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Deuteron Deuteron

Extract shape of

x(s(x) s(x))

Extract

x(s s)

x(u u d d)

Isoscalar Method

Measure Multiplicities

(π+ + π-, K+ + K-, Ks0)

Measure Asymmetries

(e-, π+ + π-, K+ + K-, Ks0)

Isoscalar MeasurementsUnpolarized Measurements Polarized Measurements For a deuteron target: Assuming isospin symmetry

& charge conjugation invariance:

Ad (x,Q2)

AdH (x,Q2)

CR

PNS (x,Q2) PS (x,Q

2)

PNSH (x,Q2) PS

H (x,Q2)

Q(x,Q2) Q(x,Q2)

S(x,Q2) S (x,Q2)

H = K+ + K-

H = Ks0

H = π+ + π-

Q u u d d

S s s

• Extract isoscalar combinations of ΔQ(x) and ΔS(x)

• Inclusive purities from PDFs (CTEQ-n, MRST, GRV…)

• Example: for Kaons, purities can be computed from the Kaon multiplicities and the pdfs.

Example: Kaon Purities

)()( zDzD KK

q

KK

q

- Using charge symmetry

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FF=Fit parametersMeasure

Multiplicities

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Flavor DecompositionUnpolarized Measurements Polarized Measurements

Proton Proton

Measure Multiplicities

(π+, π-, π0, K+, K-, Ks0)

Measure Asymmetries

(e-, π+, π-, π0, K+, K-, Ks0)

Deuteron Deuteron

Extract

xu,xd,xs,xu,xd,xs,x(ud)

- Purities depend on the unpolarized PDFs and the fragmentation functions.

- For the FFs, one can constrain them using measured pion and kaon multiplicities in the

same kinematical range from unpolarized proton and deuteron data,

- System can be solved by c2 minimization accounting for the correlations between the

various asymmetries.

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Jefferson Lab• Continuous Electron Beam Accelerator

Facility

• Upgrade in energy from 6 GeV to 12 GeV.

• Directed into Halls A, B, C, and D.

• E12-09-007 is taking place in Hall-B.

• Some of the unpolarized measurements were taken.

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Jefferson Lab CLAS12 @ 11GeV

Track resolutions:p (GeV/c) 0.003p + 0.001p2

(mr) < 1

(mr) < 3

Lumi > 1035cm-1s-1

Wide detector and physics

acceptance (current/target fragmentation)

High beam polarization 85%

High target polarization 85%

Hydrogen and Deuterium targets.

GeV/c 1 2 3 4 5 6 7 8 9 10

/K

/p

K/p

e/

HTCC

TOF

TOF

TOF

HTCC

HTCC

HTCCEC/PCAL

LTCC

LTCCRICH

LTCCLTCCRICH

LTCCRICH

Replace two LTTC

with a Ring Imaging

CHerenkov

1 RICH detector is

constructed

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CLAS12 Hybrid RICH Detector

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PhotoMultiplier Tubes

• Uses photoelectric effect• Multiplies photoelectrons using a dynode

system

• 391 mulit-anode photomultiplier tubes (MAPMTs, H12700) in RICH

• 8x8 matrix of pixels for spatial resolution => 25,024 channels

• High-speed electronics for signal processing

• Use ASIC for analog-to-digital conversion• Define thresholds for time-to-digital

conversion• Use Xilinx FPGA for parallel data acquisition• Response time of 0.5 ns• Data Rate: 10 MB/s• Overall Event Rate: 12,000 events/s 15

16F. Benmokhtar, APS 201716

Which Ones?

Assembling of the RICH

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RICH was installed in the CLAS12 spectrometer in January of 2018 and a second is under construction and will be completed by 2022.

Reconstruction programs underway then calibrations!

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Expected Precisions

Kaon Multiplicities and Frag. Func.

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Projections – Isoscalar Method

K+ + K- Ks0

F. Benmokhtar, CIPANP 2018

Corrections:

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Projections – Flavor

decomposition (1) -

10% systematics on

asymmetries

21F. Benmokhtar, CIPANP 2018F. Benmokhtar, CIPANP 2018

Corrections:

Test whether or not the light sea

is symmetrically polarized

Projections – (2) -

10% systematics on

asymmetries

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• Polarized deep-inelastic inclusive scattering(SMC)

-p elastic scattering

• Polarized Semi-Inclusive DIS (HERMES)

* 5 flavor tagging

* Isoscalar method-> published (2008) then reviewed and

published (2014), slightly positive

positive and 0 ~s

(E734 BNL)

World Data on S

• COMPASS: sidis m-NH3 (2010) compatible with zero.

• ATLAS results (2012) suggest that at small x the strangeness contribution

can be substantially larger than assumed. Phys. Rev. Lett. 109, 012001 – Published 5 July 2012

So far, the results vary widely and the uncertainties are big

“Strange quark polarization puzzle”

23F. Benmokhtar, CIPANP 2018

Corrections:

Projections – Flavor

decomposition (2) -

10% systematics on

asymmetries

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Expected Precisions x S(x)

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The systematics related to our knowledge of fragmentation functions

can further be reduced with high precision multiplicity measurements.

Test whether or not the light sea is symmetrically polarized.

Improve NLO global analysis of Helicity Parton densities and their

uncertainties.

Conclusion and Outlook

Thanks!

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Backup Slides

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- Cherenkov angle distributions for 8GeV/c pions tagged by the CERN T9 gas

Cherenkov compared with those of kaons and protons.

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Testing of MA-PMTs

- Hamamatsu H8500 and H12700 MAPMTs

- Inside the testing black-boxa Class 3b picosecond diode laser was used.Study 8x8 pixel per PMT

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