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Search for the Onset of Color Transparency in ProtonsSearch for the Onset of Color Transparency in Protons Deepak Bhetuwal

Advisor: Professor Dipangkar DuttaDepartment of Physics and Astronomy, Mississippi State University, Starkville, Mississippi, 39762, USA

ABSTRACTColor transparency (CT) is a a unique prediction of Quantum Chromodynamics (QCD) where the final (and/or initial) state interactions of hadrons with the nuclear medium are suppressed for exclusive processes at high momentum transfers.

During the spring of 2018, the experiment E1206107 to measure proton transparency was the first to run in Hall C at Jefferson Lab using the upgraded 12 GeV electron beam. Our experiment used the High Momentum Spectrometer (HMS) and new Super High Momentum Spectrometer (SHMS) in coincidence to measure 12C(e,e’p) proton knockout to extract the proton nuclear transparency with additional 1H measurements to determine the elementary process, over the range Q2 = 8 − 14.3 (GeV/c) 2 . A rise in the proton transparency as a function of Q2 is predicted to be a signature of the onset of Color Transparency.

This poster will summarize the status of the experiment since the completion of data taking and show some preliminary results.

INTRODUCTION of CT

CT EXPERIMENT - E1206107

DRIFT CHAMBER CALIBRATION

ONSET of CTSignature for the onset of CT involves rise in nuclear transparency, T

A, as a

function of the momentum transfer, Q2.

Coincidence trigger: SHMS measures protons, HMS measures electrons.

~20 days of data taking with E_beam of 6.4 GeV and 10.6 Gev with up to 60 uA of beam current.

Targets: 10 cm LH2 (Hee’p check), 6% 12C (production), Al dummy (background) .

Data collected at 4 Q2 points – 8.0 (GeV/c)2 , 9.5 (GeV/c)2 , 11.5 (GeV/c)2

and 14.3 (GeV/c)2

Jun 23, 2020

JEFFERSON LAB

EXPERIMENTAL HALL C

A clear signal for the onset of CT for baryons would show the transition from the nucleon-meson picture to quark-gluon degrees of freedom → Onset is signature for QCD degrees of freedom in nuclei.

Not predicted by strongly interacting hadronic picture but arises in picture of quark-gluon interactions.

QCD: Color field of singlet objects vanishes as size is reduced.

A(e, e’p)

QCD prediction

Traditional nuclear physics prediction

PION

RHO

New Super High Momentum Spectrometer (SHMS) HB, 3 Quads, Dipole [HB,Q1,Q2,Q3,D]

P0 → 1 - 11 GeV/c , dP/P → (0.5 -1.0) * 10-3

Acceptance:5 msr, 30% ; 5.50 < θscattering

< 400

High Momentum Spectrometer (HMS) 3 Quads, Dipole [Q1,Q2,Q3,D]

P0 → 0.5 - 7.5 GeV/c , dP/P → (0.5 -1.0) * 10-3

Acceptance: 6.5 msr, 18% ; 12.50 < θscattering

< 900

Well shielded detector HUTS in both HMS and SHMS

BARYON

No .

of

Cou

n ts

Drift Distance (cm)

No.

of

Cou

n ts

Residual (cm)

CALORIMETER CALIBRATION

No .

of

Cou

n ts

De l

ta (

%)

Normalized Track Energy Normalized track energy

HODOSCOPE CALIBRATION

De l

ta (

%)

Beta Beta

No.

of

Cou

n ts

TRANSPARENCY

SUMMARYExperiment took 4 data points in Q2 regime (8-14.3) GeV2, region overlaps with Brookhaven data.

First experiment to run in the 12 GeV era in Hall C and to take data using the SHMS and HMS. Analysis to extract the final transparency is ongoing → full results expected by the end of the year!

REFERENCES / ACKNOWLEDGMENTS[1] D. Dutta, K. Hafidi, and M. Strikman, Prog. Part. Nucl. Phys. 69, 1 (2013).[2] D. Dutta and K. Hafidi, Int. J. Mod. Phys. E21, 1230004 (2012).

Thanks to Prof. Dipangkar Dutta for his kind help throughout, Dr. Holly Szumila-Vance, John Matter and to the entire CT collaboration team for their continuous support.

This work is supported by U.S. DOE Grant Number: DE-FG02-07ER41528

CT is basically consequence of squeez-ing and freezing, and it can be summarized with mainly 3 processes: PLC creation, it’s propagation in and interaction with the nuclear medium.

YIELD RATIO - DATA/SIMULATION

EFFICIENCIES OF DETECTORS

e-

Emiss < 80 MeVPmiss < 300 MeV

Emiss < 100 MeVPmiss < 100 MeV

CT HUNTCT well established at high energies essential for scaling at low x in Deep Inelastic Scattering (DIS).

Onset of CT has been measured in mesons but not in baryons.

Onset is signature for QCD degrees of freedom in nuclei.

CUT VARIATION STUDY

Mean of the % difference in TransparencyRange of the the % difference in Transparency

ΔT/T = % difference in TransparencyVariation # = # of different transparencies while varying each cut by +/- 10%

LUMINOSITY SCAN ON 12C (SHMS)

LIVE TIME