L-T  separated  Kaon  Production  Cross  Sections  

from  5-11  GeVSpokespersons:  Garth  Huber,  Tanja  Horn,  Pete  Markowitz

Samip Basnet  (U.  Regina)  and  Salina  Ali  (CUA)

For  E12-09-011  Collaboration

1SAPIN-2016-0031

Outline

• E12-09-011:  Motivations  and  Goals• Kinematic  Coverage• Experimental  Constraints  • Runplan• Rate  Studies

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E12-09-011  Motivation• The  p(e,e’K+)Λ,Σ° reactions  are  important  tools  in  our  study  of  hadron  structure.

• Flavor  degree  of  freedom  is  introduced  with  the  addition  of  strange  quark  provides  important  information  for  QCD  model  building,  as  well  as  for  our  improved  understanding  of  the  basic  coupling  constants  needed   in  nucleon-meson  and  quark  models.

K+

• The  SHMS+HMS  will  allow  for  the  first  time  high  quality  L/T  separated  data  for  exclusive  K+ production  above  the  resonance  region.

• Since  the  statistical  uncertainties  for  K+ production  are  expected  to  be  larger  than  π+ production,  larger  systematic  uncertainties  also  can  be  tolerated.    → L/T commissioning  experiment  with  coincidences  +  PID.

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The  QUESTION:• Can  “kaon  cloud”  of  the  proton  be  used  in  the  same  way  as  the  pion  to  extract  kaon  form  factor  for  Q2>0.2  GeV2 via  p(e,e’K+)Λ?

• Kaon  pole  further  from  kinematically  allowed   region.

)()()(

2 22222

2

QFegkmttQ

KNKK

L Λ−

−≈σ

Goal  1:  Study  of  K+ Reaction  MechanismTHE  METHOD:• SHMS+HMS  coincidence  acceptance  allows  for  simultaneous  studies  of  Λ and  Σ° channels.

• Kaon-pole  dominance  test  through

• Should  be  similar  to  ratio  of                g2pK Σ /g2pKΛ coupling  constants  if                t-channel  exchange  dominates.

)()(0*

0*

Λ→

Σ→+

+

KpKp

L

L

γσγσ

Fπ,K

π, K, etc

φ

φ

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Kaon  Form  Factor• Measure  the  –t  dependence  of  the  p(e,e’K+)Λ,Σ° cross  section  at  fixed  Q2 and  W>2.5  GeV  to  search  for  evidence  of  K+ pole  dominance  in  σL

• If  warranted  by  the  data,  extract  the  Q2 dependence  of  the  kaon  form  factor  to  shed  new  light  on  QCD’s  transition  to  quark-gluon  degrees  of  freedom.

• Even  if  we  cannot  extract  the  kaon  form  factor,  the  measurements  are  important.• K+Λ and  K+Σ˚ reaction  mechanisms  provide  valuable  information  in  our  study  of  hadron  structure

– Flavor  degrees  of  freedom  provide  important  information  for  QCD  model  building  and  understanding  of  basic  coupling  constants

Projected  Uncertainties  for  FK

For  VGL/Regge  calculation,  assume  Λ2K=0.67  GeV2,  andΛ2K*=1.5  GeV2,

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Goal  2:  Q-n Scaling  Tests• Separated  p(e,e’K+)Λ,Σ° cross  sections  allow   investigations  of  the  transition  from  hadronic  (baryons+mesons)   to  partonic  (quarks+gluons)   degrees  of  freedom  in  exclusive  processes.

Factorization

GPD

π, K, etc.φ

• As  it  is  not  known  how  high  Q2 is  needed  for  the  factorization  theorem  to  apply,  it  is  necessary  to  first  test  that  the  regime  of  validity  has  been  reached.• This  can  be  done  by  comparing  the  Q2 variation  of  the  cross  section  against  the  prediction  of  Hard  QCD.

• K+ electroproduction   adds  a  new  dimension  to  these  studies.    Virtually  nothing  is  known  concerning  QCD  factorization  when  strangeness  is  in  play.

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Scaling  Measurement  Goalsn Measure  the  Q2 dependence  of  the  p(e,e’K+)Λ,

p(e,e’K+)Σ cross  sections  at  fixed  xB and  –t to  search  for  evidence  of  hard-soft  factorizationn Separate  the  cross  section  components:  L,  T,  LT,  TT  n Highest  Q2 for  any  L/T  separation  in  π+,K+ electroproductionn Can  only  learn  about  GPDs  if  soft-hard  factorization  appliesn If  transverse  contributions  are  large,  the  accessible  phase  space  may  be  limited

n A  stringent  test  is  the  Q2-dependence  of  the  p(e,e’K+)Λcross  sections:Ø σL scales  to  leading  order  as  Q-6.Ø σT scales  as  Q-8.Ø As  Q2 becomes  large:  σL >>  σT.

Fit:  1/Qn

1/Q8

1/Q6

1/Q4

p(e,e’K+)ΛxB=0.25

Projected  Uncertainties  

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Kinematic  CoverageØ Measure  the  separated  cross-sections  at  varying  –t  and  xB to  study  the  reaction  mechanism  (and  possibly  extract  the  FK)

Ø Measure    the  L-T  separated  cross-sections  for  p(e,e’K+)Λ(Σ0)  reaction  at  two  fixed  values  of  –t  and  xBü Q2 coverage  is  a  factor  of  2-3  larger  compared  to  6  GeV  at  small  –t  

xB Q2(GeV2)

W(GeV)

|  t  |(GeV/c)2

0.1-0.2 0.4-3.0 2.5-3.1 0.06-0.20.25 1.7-3.5 2.5-3.4 0.20.40 3.0-5.5 2.3-3.0 0.5

Q2  =  3.0  GeV2 is  optimized  to  be  used  for  both  t-channel  and  Q-n scaling  

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Experimental  Constraints

§ Hall  C:  Ebeam(GeV)  =  

§ SHMS for  Kaon  detectionü Kaon  angles:                  – 18.4°ü Kaon  momenta:    2.6  – 7.1  GeV/c

§ HMS for  scattered  electron  detectionü Electron  angles:  10.6° – 31.3°ü Electron  momenta:  0.9  – 5.1  GeV/c

§ Particle  Identification:ü Aerogel  Cherenkov  detector  for  proton/kaon separation

ü Heavy  Gas  Cherenkov  detector  for  pion/kaon separation

6.4, 8.6,  10.63.8,  5.0,  5.5,  7.5,  8.2,  9.3  

w/  Standard  Tune

require  Special  Tune

5.5° The  smallest  angle  setting  for  SHMS

First  two  arms  L-T  separation  commissioning  experiment!  

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Runplanv Period  1:

v Period  2:

Q2(GeV2)

W(GeV)

xB | t  |(GeV) 2

ε Ebeam(GeV)

0.4 2.45 0.07 0.06 0.68 4.950.4 2.45 0.07 0.06 0.41 3.801.7 2.45 0.25 0.24 0.60 5.64

1.7 2.45 0.25 0.24 0.86 8.762.0 3.14 0.18 0.14 0.58 8.762.0 3.14 0.18 0.14 0.75 10.923.0 2.32 0.40 0.53 0.63 6.603.0 2.32 0.40 0.53 0.88 10.923.0 3.14 0.25 0.22 0.69 10.923.5 3.37 0.25 0.22 0.56 10.924.4 2.74 0.40 0.51 0.74 10.925.5 3.02 0.40 0.50 0.56 10.92

w/  Special  Tune

w/  Standard  Tune

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vPeriod  3:1.25 3.14 0.12 0.08 0.49 7.501.25 3.14 0.12 0.08 0.70 9.342.0 3.14 0.18 0.14 0.40 7.503.0 3.14 0.25 0.22 0.40 8.193.5 3.37 0.25 0.22 0.40 9.344.4 2.74 0.40 0.51 0.48 8.195.5 3.02 0.40 0.50 0.37 9.34

w/  Special  Tune

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Spectrometer  Acceptance  Cuts  Applied

For  HMS:|hsdelta|  <  8.0;;  |hsxptar|  <  0.080;;  |hsyptar|  <  0.035

For  SHMS:|ssdelta|  <  15.0;;  |ssxptar|  <  0.040;;  |ssyptar|  <  0.024

Diamond  Cut  for  Λ:

W W

Q2 Q2

Q2  =  2.0W  =  3.14@  low  ε

Q2  =  2.0W  =  3.14@  high  ε

Q2  =  2.0W  =  3.14@  low  ε

Simulated  Acceptance  and  Kinematics  StudiesData  simulated  using  SIMC

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Coincidence  Rate  StudiesSample  Missing  Mass  Resolution  

from  the  simulated  dataModels  Comparison

Two  models  used  for  rate  estimation:v “Old  Kaon”:  empirical  model  from  fits  of  previous  kaon  electroproduction global  data

[D.  Koltennuk (1999),  T.  Horn  (2007)]

v VR:  improved  model  featuring  Reggeizedbackground  amplitudes

[Vrancx and  Ryckebusch (2014),  Corthals (2007)]  

Good  News,  everybody!

Both  the  models  are  predicting  higher  rates  than  the  proposal!

Expected  Real  Rates  with  SIMC  @  70  μA  on  10cm  target  

low  ε high  ε

Q2  =  2.0W  =  3.14@  low  ε

Λ

Σ0

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Singles  Rates  and  Accidental  Coincidences  Singles  rates  calculated  using  following  programs§ Wiser:  a  parameterization  of  hadron  electroproduction cross-sections  by  Steve  Rock  (SLAC)

§ Electron  Scattering:  Bosted/Christy  parameterization  of  the  elastic  and  inelastic  electron  cross-sections

Singles  RatesFor  SHMS: For  HMS:Particles Rate  Range

(kHz)p 4-160π+ 10-1000K+ 5-125

Particles Rate  Range(kHz)

e 1-205π- 1-255K- 0.04-7

Accidental  Coincidencesfor  low  Q2    @  70μA  and  10cm  target  length    

v All  accidentals  are  calculated  for  70μA  of  beam  current  at  10cm target   length  with  40ns coincidence  window

v Improved  accidentals  does  not take  into  account  300:1  π+  &    p  rejection  since  we  don’t  want  Cherenkovs  in  the  trigger

v The  accidentals  are  high  at  low  Q2    but  the  proposal  suggests  using  lower  beam  current  and/or  smaller  target  length

Q2(GeV2)

ε R(acc)(Hz)

0.40 0.41 829

0.40 0.68 1636

1.25 0.70 1410

1.70 0.86 1297

2.00 0.58 1624

Accidentals  for  higher  Q2are  well  below  500  Hz!!