7 - 11 June 2004L. Benussi - DAFNE 2004 First results on hyper-nuclear spectroscopy from the FINUDA...

7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004

First results onFirst results onhyper-nuclear spectroscopy hyper-nuclear spectroscopy from the FINUDA experimentfrom the FINUDA experiment

at DAat DANENE

Luigi BenussiLuigi BenussiINFN, Laboratori Nazionali di FrascatiINFN, Laboratori Nazionali di Frascati

On behalf of FINUDA CollaborationOn behalf of FINUDA Collaboration

DAFNE 2004 - Frascati, June 4-8,2004DAFNE 2004 - Frascati, June 4-8,2004


•Bari University and I.N.F.N. Bari, ItalyBari University and I.N.F.N. Bari, Italy

•Brescia University and I.N.F.N. Pavia, ItalyBrescia University and I.N.F.N. Pavia, Italy

•KEK, JapanKEK, Japan

•Laboratori Nazionali di Frascati I.N.F.N., ItalyLaboratori Nazionali di Frascati I.N.F.N., Italy

•Pavia University and I.N.F.N. Pavia, ItalyPavia University and I.N.F.N. Pavia, Italy

•Seoul National University, KoreaSeoul National University, Korea

•Shahid Beheshty University, Teheran, Iran Shahid Beheshty University, Teheran, Iran

•Torino University and I.N.F.N. Torino, ItalyTorino University and I.N.F.N. Torino, Italy

•Torino Polytechinc and I.N.F.N. Torino, ItalyTorino Polytechinc and I.N.F.N. Torino, Italy

•Trieste University and I.N.F.N. Trieste, ItalyTrieste University and I.N.F.N. Trieste, Italy

•TRIUMF, Vancouver, Canada TRIUMF, Vancouver, Canada

The FINUDA collaborationThe FINUDA collaboration


50 Years after the discovery of the50 Years after the discovery of thefirst hyper-nucleus, FINUDA has started first hyper-nucleus, FINUDA has started

its production of strange nuclei in Frascatiits production of strange nuclei in Frascati

Talk outlines:Talk outlines:• Performances and events reconstructionPerformances and events reconstruction• First preliminary results on hyper-nuclear First preliminary results on hyper-nuclear

spectroscopyspectroscopy


FINUDAFINUDAFIFIsicasica NU NUclearecleare aa DADANENE

The The ’s’sproduced by DAproduced by DANE provide a unique “KNE provide a unique “K beam”…. beam”….

1.1. Monochromatic, low momentum (127 MeV/c)Monochromatic, low momentum (127 MeV/c)

2.2. trigger tagging Ktrigger tagging Kstop stop event through the associate Kevent through the associate K

3.3. no hadronic backgroundno hadronic background

…….that can be stopped in thin targets to produce hypernuclei .that can be stopped in thin targets to produce hypernuclei

KKstop stop + + AAZ Z AA

Z + Z +


FINUDA main physics programFINUDA main physics program

• Production of Production of -hyp. : K-hyp. : Kstop stop + + AAZ Z AA

Z + Z +

– spectroscopy of hyp. via the spectroscopy of hyp. via the promptprompt momentum momentum

• Decay of Decay of -hyp.-hyp.

mesonic decays is Pauli blockedmesonic decays is Pauli blocked

non-mesonic decays prevalentnon-mesonic decays prevalent

• Lifetime of Lifetime of -hyp.-hyp.

• Search for neutron rich Search for neutron rich -hyp.-hyp.

0; np

nnnnpp ;

FINUDA can study

FINUDA can study

simultaneously

simultaneously

hyp. spectroscopy

hyp. spectroscopy

and hyp. decays

and hyp. decays


3 targets of 3 targets of 1212C C 2 targets of 2 targets of 66Li Li 1 target of 1 target of 77LiLi1 target of 1 target of 2727AlAl1 target of 1 target of 5858VV

OSIMOSIM

ISIMISIM

TOFINOTOFINO

TargetsTargets

Beam pipeBeam pipe

Interaction-Target regionInteraction-Target region


Segmented Segmented targettarget in 8 different modules: in 8 different modules:

2 of 2 of 66Li, 1 of Li, 1 of 77Li, 3 of Li, 3 of 1212C, 1 of C, 1 of 2727Al and 1 of Al and 1 of 5151VV

66LiLi: Source of : Source of 44He and He and 55

He (He (66Li unstable); study of the decay of light Li unstable); study of the decay of light

hypernuclei (never examined);hypernuclei (never examined);

77LiLi: Comparison with the : Comparison with the 66Li target, available data of poor quality w.r.t Li target, available data of poor quality w.r.t

FINUDA performance;FINUDA performance;

1212CC: Reference target for spectroscopy and weak decays studies, search : Reference target for spectroscopy and weak decays studies, search

for states weakly excited, for states weakly excited, 10 1055/K/Kstopstop (present limit 10 (present limit 104 4 /K/Kstopstop););

2727AlAl: Never studied before; measurement of the capture rate in the : Never studied before; measurement of the capture rate in the

medium A hyper-nuclei;medium A hyper-nuclei;

5151VV: No measurements available with K: No measurements available with K-- at rest, useful for weak decay at rest, useful for weak decay

studies; important to assess the capture rate for the medium and heavy studies; important to assess the capture rate for the medium and heavy

hyper-nuclei;hyper-nuclei;

Target ChoiceTarget Choice


e+

e

ee invariant mass (GeV/c)

Ks

e+e e+e

FINUDA performances: FINUDA performances: Bhabha eventBhabha event


FINUDA performances: FINUDA performances: Hyper-nuclear formation eventHyper-nuclear formation event

+

-

K-

K+

+

-


FINUDA performances: FINUDA performances: Hyper-nuclear formation and decay eventHyper-nuclear formation and decay event


KK stopping point stopping point distributiondistribution

Scatter plot of the reconstructed y vs x Scatter plot of the reconstructed y vs x coordinates of the Kcoordinates of the K stopping points stopping points

– most external octagon: 8 target modules, most external octagon: 8 target modules, where most of the Kwhere most of the K stop. stop.

– Inner layers: stops on the microstrip ISIM Inner layers: stops on the microstrip ISIM modules which give us an additional target: modules which give us an additional target: 2828

Si can be studied Si can be studied

7Li

6Li

27Al 51V

12C12C

12C

6Li

Isim 8

Isim 7

Isim 2

Isim 1


Momentum distribution of KMomentum distribution of K++ charged decay productscharged decay products

K+ +

K+ + o

KK++ ++

KK++ ++oo

The width of the The width of the ++ peak gives a peak gives a momentum momentum resolution of: resolution of:

p/p< 0.9% p/p< 0.9%

(Goal (Goal p/p< 0.35%)p/p< 0.35%)


Event and track selectionEvent and track selection Selection criteria for Selection criteria for -- Candidates from hypernuclear formation: Candidates from hypernuclear formation:

• negative track from Knegative track from K vertex; vertex;• 4 points/track, in detectors:4 points/track, in detectors:

Outer microstrip OSIMOuter microstrip OSIMfirst layer LMDCfirst layer LMDCsecond layer LMDCsecond layer LMDCStraw Tubes tripletStraw Tubes triplet

• forward track forward track (more clean events….backward tracks will be used mainly for decays study)(more clean events….backward tracks will be used mainly for decays study); ; • angle w.r.t. target 0angle w.r.t. target 0oo 70 70oo;;• momentum corrected for the energy loss in the target material momentum corrected for the energy loss in the target material

crossed;crossed;• Quality cuts onQuality cuts on track fitting;track fitting;


reconstructed momentum spectrumreconstructed momentum spectrumin the 8 targetsin the 8 targets

Clean hypernuclear structures Clean hypernuclear structures present in all targetspresent in all targets

sel. sel. cutscuts


Target N.1 Target N.1 1212C nucleusC nucleus1212C is the reference Nucleus C is the reference Nucleus

In the following data only from In the following data only from 1212C target (target n.1) C target (target n.1) about 20% of the available statistics for about 20% of the available statistics for 1212CC

Different targets have different systematic mainly due to the geometrical alignment of Different targets have different systematic mainly due to the geometrical alignment of the detectors, that are currently being improved…. the detectors, that are currently being improved….

The measured momentum spectrum is transformed into binding The measured momentum spectrum is transformed into binding energy (Benergy (B) spectrum of the lambda) spectrum of the lambda

BB=M=MA-1A-1+M+MMMA A M MKK+M+M +T+T


Background reactions: Background reactions: - spectra- spectra

K- n -

p -

K- p+ -

K- p- +

- n -

K- (NN)- N - n -

K- n0 -

TOT

Background reactions giving a Background reactions giving a following K following K Nucleus Nucleus interactions have been simulated in the apparatusinteractions have been simulated in the apparatus with with FINUDA Monte Carlo:FINUDA Monte Carlo:


(K(K--stopstop, , -)-) 1212

C spectrum C spectrum

• Simulated background particles have been Simulated background particles have been reconstructed andreconstructed and selected following the selected following the same selection criteria as for the hyper-same selection criteria as for the hyper-nucleus formation nucleus formation candidates candidates

• The shape of the background simulated The shape of the background simulated and reconstructed spectrum is and reconstructed spectrum is parameterized and subtracted from the parameterized and subtracted from the experimental spectrum.experimental spectrum.

• Resolution (Resolution (E E =600keV) set by peak #2 =600keV) set by peak #2 p/p p/p 0.6% 0.6%

#2

#1

FINUDA P

relim

inar

y


Exclude region between peaks Exclude region between peaks #1 , #2. #1 , #2. We fit with 2 gauss with We fit with 2 gauss with EE=600 =600 keV fixed keV fixed There is more than 1 object in There is more than 1 object in #2 (?)….#2 (?)….

…….try to fit peak #2 with 2 .try to fit peak #2 with 2 gauss….Seems better but….gauss….Seems better but…. ……add a third gauss for the add a third gauss for the

peak #2peak #2…….Now better fit. .Now better fit.

#1

#2

preliminary

preliminary

preliminary

FINUDA preliminary 12C spectrum

#1

#2

#1

#2


• Partial statistics, only one of the Partial statistics, only one of the three three 1212C targets C targets • Best fit with the sum of 4 gauss Best fit with the sum of 4 gauss distributions, 1 for the ground distributions, 1 for the ground state peak (#1), 3 needed to state peak (#1), 3 needed to describe the excited state peak describe the excited state peak (#2) (#2) • Region between main peaks Region between main peaks excluded from fit.excluded from fit.

preliminary#2

#1

Capture Rates: #1 ground state: ~ 1.8x10-3/K-

stop

#2 excited state: ~ 3.3x10-3/K-stop

FINUDA preliminary FINUDA preliminary 1212C spectrumC spectrum

#3#4


1212C spectroscopy: C spectroscopy: FINUDA vs KEKFINUDA vs KEK

H.Hotchi, Phys.Rev. C 64 (2001) 044302

Previous results: KEK E369Previous results: KEK E369Energy resolution Energy resolution 1.45 MeV FWHM 1.45 MeV FWHM production reaction (production reaction (KK

FINUDA preliminary FINUDA preliminary Energy resolution Energy resolution 1.4 MeV FWHM 1.4 MeV FWHM production reaction (Kproduction reaction (K

stopstop, , ) )

#1

#2 = #5

#3 = #6

#4 = ?


ConclusionsConclusions• FINUDA HAS SUCCESSFULLY ENDED the FIRST FINUDA HAS SUCCESSFULLY ENDED the FIRST

DATA TAKING PERIOD COLLECTING 30XDATA TAKING PERIOD COLLECTING 30X10106 6

EVENTSEVENTS

• FINUDA preliminary results, with partial statistics FINUDA preliminary results, with partial statistics

(~1/5) and not yet final momentum resolution (~1/5) and not yet final momentum resolution

(~40% worst), are already at the same level of (~40% worst), are already at the same level of

the best published results on hyper-nuclear the best published results on hyper-nuclear

spectroscopyspectroscopy

7 - 11 June 2004L. Benussi - DAFNE 2004 First results on hyper-nuclear spectroscopy from the FINUDA...

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