Spectroscopy of
Download
1 / 34

Introduction - PowerPoint PPT Presentation


  • 294 Views
  • Updated On :

Spectroscopy of  -Hypernuclei by Electroproduction HNSS/HKS Experiments at JLAB L. Tang Hampton University & JLAB. FB18, Brazil, August 21-26, 2006. J P =1/2 +. S = 0. S = -1. S. Q. S = -2. n (udd). p + (uud).  + (uus).  - (dds).  - (dss).  0 (uss). , 0 (uds). I.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Introduction ' - mike_john


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Spectroscopy of -Hypernuclei by ElectroproductionHNSS/HKS Experiments at JLABL. TangHampton University& JLAB

FB18, Brazil, August 21-26, 2006


Introduction yn interaction l.jpg

JP=1/2+

S = 0

S = -1

S

Q

S = -2

n

(udd)

p+

(uud)

+

(uus)

-

(dds)

-

(dss)

0

(uss)

,0

(uds)

I

Introduction – YN Interaction

  • B-B interactions are fundamental in our understanding on the formation of the world – Nuclear Matter, Neutron Stars, …

  • Our current knowledge is basically limited at the level of S = 0 (n and p)

  • Study S ≠ 0 B-B interactions (YN and YY) is a MUST in order to extend our knowledge to include as well as reach beyond strangeness and seek an unified description of B-B interaction

  • Due to the short lifetime of Y, direct study of YN interactions is almost impossible


Slide3 l.jpg

Introduction – Hypernuclei

  • Hypernucleus–A nucleus with one or more nucleons replaced by hyperon, Λ, Σ, …,through elementary production process

  • Unique gate way to study S ≠ 0B-B interaction: YN interaction embedded in a nuclear mean field, a rich laboratory to study YN interactions with the method of NUCLEAR PHYSICS

  • New degree of freedom in nucleus –StrangenessChallenges the limit of conventional nuclear models of hadronic many-body system but also open doors to new or hidden aspects in the “traditional” nuclear physics


Introduction hypernuclei l.jpg
Introduction – -Hypernuclei

  • -hypernuclei are the most stable ones(S = -1)

  • Novel features of -hypernucleus –N Interaction

    Absence of long range OPE between Λ and N due to conservaison of isospin in strong interaction, thus itsignifies

    - Higher mass meson exchanges that are over shadowed by the

    dominant OPE force in N-N interactions in the traditional nuclear

    nuclear physics

    - Sizable charge asymmetry (p and n)

    - Intermediate Λ-Σ coupling and significant three-body forces

    (ΛNN) with two-pions exchange


Slide6 l.jpg

Understanding the N-N Force

In terms of mesons and nucleons:

Or in terms of quarks and gluons:

V =


Slide7 l.jpg

-Hypernuclei Provide Essential Clues

For the N-N System:

For the L-N System: Long Range Terms Suppressed

(by Isospin)


Introduction hypernuclei8 l.jpg
Introduction – -Hypernuclei

  • Absence of Pauli Blocking–, like an “impurity”, has full access to all levels of nuclear interior structures, thus a better illumination to explore the nuclear interior

  • Stabilized states with narrow width– decays weakly, thus allowing precision spectroscopy and theory descriptions

  • Opening issues:

    - Precise description of -Nucleus potential (spin dependent

    interactions)

    VΛN(r) = Vc(r) + Vs(r)(SΛ*SN) + VΛ(r)(lΛN*SΛ) + VN(r)(lΛN*SN) + VT(r)S12

    - To what extend the  remains as a single particle, effective vs

    exact models

    - Short range nature of N interaction and density dependency


Model productions of hypernuclei l.jpg

Particle

Particle hole

P-

OR

P

OR

S

OR

Model Productions of -hypernuclei

  • (K-, -) –Nature parity, low spin substitutional

    states due to low momentum transfer,

    high yield

  • (+, K+) –Nature parity, high spin stretched states

    due to high momentum transfer

  • (e, e’K+) –Unnature parity, high spin stretched

    states dueto high momentum transfer

    and the spin covered by the virtual

    photons


Slide10 l.jpg

Spectroscopy – Low lying A=12 system ( in s shell)

(e,e’K+) Reaction

(π+, K+) Reaction

1-

1-

3/2-

5.02

3/2-

4.80

2-

2-

5/2-

4.45

2-

2-

4.32

5/2-

0-

0-

1/2-

2.12

2.00

1/2-

1-

1-

~0.1

~0.1

2-

2-

0.00

3/2-

0.00

3/2-

1-

1-

0.0

0.0

JP

JP

MeV

MeV

12B

12C

11B

11C

Complementary and charge symmetry breaking


L single particle potential l.jpg

KEK E140a

Hasegawa et. al., PRC 53 (1996)1210

L single particle potential

Energy resolution is very limited by using hadronic beam – 1.5 MeV FWHM

Hotchi et al., PRC 64 (2001) 044302

Textbook example of

Single-particle orbits in nucleus

L Single particle states

→L-nuclear potential

depth = -30 MeV →VLN < VNN


Slide12 l.jpg

Existing 12C(p+,K+)12LC spectra

BNL 3 MeV(FWHM)

KEK E369 1.45 MeV(FWHM)

High resolution, high yield, and systematic study is essential and is the key to

unlock the “gate”

KEK336 2 MeV(FWHM)


Slide13 l.jpg

Thomas Jefferson National

Accelerator Facility

(TJNAF or JLAB)

www.jlab.org

Virginia

Location in U.S.A.


Slide14 l.jpg

East Arc

FEL

South

Linac

+400MeV

North

Linac

+400MeV

Continuous Electron Beam Accelerator Facility (CEBAF)

MCC

West Arc

Injector

A

CH

C

B


Electroproduction of hypernuclei in hall c at jlab l.jpg
Electroproduction of -hypernucleiin Hall C at JLAB

  • High precision beam → high resolution spectroscopy

  • High intensity and 100% duty factor → Overcome low cross section for high yield which is essential to study heavy hypernuclei

  • Advantage: High resolution and high yield

  • Challenges: Extremely high particle rates


Slide16 l.jpg

e

e’

K+

N

A

A

→ Coincidence of e’ and K+

→ Keep ω=E-E’ low (K+ background)

→ Maximize Γ –- e’ at forward angle

→ Maximize yield –- K+ at forward

angle

Key Considerations in Electroproduction

d2σ/dΩk is completely transverse as Q2 → 0


Slide17 l.jpg

Side View

Q

K+

Target

_

D

D

Splitter

Magnet

SOS Spectrometer(QDD)

Electron Beam

_

Q

1.864 GeV

K+

1.2GeV/c

D

D

Target

Local Beam Dump

e’

Enge

0.3GeV/c

Split-Pole

Focal Plane

Spectrometer

( SSD + Hodoscope )

Beam Dump

1m

0

First Pioneer Experiment - HNSS

Year 2000

Tagged e’ at 0o!


Hnss a great challenge l.jpg
HNSS: A Great Challenge

  • Low resolution of the existing SOS spectrometer (p/p ~7x10-4 FWHM only)

  • Small solid angle acceptance (SOS has 4.5 msr)

  • Extremely high electron rate (200 MHz) at 0o

  • Can only use extremely low luminosity (20mg/cm2 target and 0.6A beam current)

  • High accidental coincidence background rate

Goal: Aim to the future and learn experiences


0 spectrum for energy calibration l.jpg
Λ (Σ0) Spectrum for Energy Calibration

p(e,e’K+)Λ

p(e,e’K+)Σ0

12C(e,e’K+)(Q.F.)

Accidentals

Beam time: 170 hours


Achievement 12 c e ek 12 l b hnss l.jpg
Achievement: 12C(e,eK+)12LB (HNSS)

11B(gs)×L(0s)

11B(gs)×L(0p)

Resolution

1.5 MeV FWHM

by (p+,K+)

750 keV FWHM

by (e,e’K+)

a month data

Beam time: 450 hrs

Calc. by Motoba & Miliner


Spectroscopy of a 7 systems 7 l he neutron rich l.jpg
Spectroscopy of A=7 Systems – 7LHe (neutron rich)

~240 hrs test

Bound g.s. !?


Jlab hks experiment 2005 l.jpg
Jlab HKS experiment (2005)

High-resolution ~400 keV (factor of 2 improvement)

High yield rates High yield

Better S/A ratio ~5 times improvement

  • 12C(e,eK+)12LB

    • demonstrate the mass resolution & hypernuclear yield.

    • core excited states and splitting of the pL-state of 12LB….

    • Mirror symmetric L hypernuclei 12LC vs. 12LB

  • 28Si(e,e’K+)28LAl

    • Prove the (e,e’K+) spectroscopy is possible for the medium-heavy target possible.

    • precision 28LAl hypernuclear structure and ls splitting of p-state….

Explore hadronic many-body systems with strangeness

through the reaction spectroscopy by the (e,e’K+) reaction

Immediate Physics goals


Key technical approaches of hks l.jpg
Key Technical Approaches of HKS

  • Electron arm

    • Tilt method for the electron arm

      • Suppress Brems electrons by 104 times

      • Need higher order terms of the transfer matrix

  • Kaon arm (Replace SOS by HKS)

    • High Resolution Kaon Spectrometer (HKS)

      • High resolution (2 times) & Large solid angle (3 times)

      • Good particle ID both in the trigger and analysis

Need sophisticated calibrations and analyses


Tilt method l.jpg
Tilt Method

(1) Brems e’

(2) Virtual photon

Associated e’

(1/1000)

(3) Moeller

scattering

  • Scattered electrons (0.2 to 0.4 GeV/c)

    • (1)from bremsstrahlung

    • (2)associate with virtual photons

    • (3) from Møller scattering

Tilt e-arm by 7.75 deg. vertically

with respect to splitter & K-arm

  • Singles rate of e-arm

    • 200 MHz → 3 MHz

  • with

  • 5 times Target thickness

  • 50 times Beam intensity

Compared to E89-009

Better Yield and S/A

Medium-heavy hypernuclei can be studied


Layout of the hks setup 2005 l.jpg

Layout of the HKS setup 2005

2 x 10-4(FWHM)

16 msr with splitter

4 x 10-4(FWHM)

Tilt 7.75 degrees


Hks 2005 l.jpg
HKS: 2005

  • Installed in 4 months (Feb. to May)

  • Commissioning in 1.5 months

  • Data taking in 2 months (near end of Sept)

  • Data taken for

    -  &  production (CH2, calibration)

    - 12B spectroscopy (C, calibration and physics)

    - 28Al spectroscopy (28Si, primary physics)

    - 6,7He, 9Li, and10,11Be (short runs, yield test)

    - 51Ti and 89Sr (short runs, yield test)


Hks analysis l.jpg
HKS: Analysis

  • Still very preliminary

  • Current stage focuses on calibration and optimization of common kinematics and optics

  • Future stages include (1) target straggling loss for individual targets and fine optical tune and (2) beam energy and on target position studies and possible corrections


Slide29 l.jpg

p(e,e’K+)&0 used for kinematics and optics calibration

HKS-JLAB

CH2 target

~ 70 hours

Preliminary

Counts (0.4MeV/bin)

B < 150keV/77 MeV

0

Events from C

Accidentals

B (MeV)


Slide30 l.jpg

12C(e,e’K+)12B used for kinematics and optics calibration

JLAB – HKS

~ 90 hrs w/ 30A

s

Preliminary

p

C.E. #1

C.E. #2

Counts (0.2 MeV/bin)

Current width:

670 keV FWHM

Accidentals

B- Binding Energy (MeV)


Slide31 l.jpg

28Si(e,e’K+)28Al – First Spectroscopy of 28Al

Preliminary

JLAB – HKS ~ 140 hrs w/ 13A

s

d ?

p

C.E. ?

Counts (0.25 MeV/bin)

Accidentals

B- Binding Energy (MeV)


Slide32 l.jpg

7Li(e,e’K+)7He – First Observation of ½+ G.S. of 7He

JLAB – HKS ~ 30 hrs

Preliminary

B (g.s.) = -4 MeV

1 to 1.4 MeV less bound than theory prediction!

s (1/2+)

Counts (0.4 MeV/bin)

Accidentals

B- Binding Energy (MeV)


Hks hes e05 115 heavy hypernuclei l.jpg

NEXT & FUTURE

HKS-HES (E05-115) - Heavy Hypernuclei

  • Replace Enge by new HES spectrometer with larger acceptance

  • Use higher beam energy (> 2.1 GeV)

  • Obtain 30 times more yield gain over HKS experiment but the same background rate

  • Improve another 5 times better S/A ratio for clean spectroscopy

  • Study 51Ti and 89Sr in detail

  • Study p-shell systems with high statistics in very short running time

  • Current schedule: installation starts in summer of 2008 all equipment will be ready by the end of 2007


Summary l.jpg
Summary

  • The first experiment HNSS proved the potential to study hypernuclear spectroscopy with high precision using the CEBAF beam and (e,e’K+) reaction at JLAB

  • The HKS experiment has successfully demonstrated that such a high precision study can be carried out with high yield and heavy systems can be studied with an optimized experiment design

  • The next phase experiment HKS/HES will be carried out in the period of 2008-2009

  • The new system and the hypernuclear program will continue after the 12 GeV upgrade in Hall A

New Era of Hypernuclear Spectroscopy !


ad