11

FINUDA Status ReportFINUDA Status Report

30th Scientific Committee Meeting

LNF, 23.05.05

A. Filippi – INFN Torino

22

Layout of the talkLayout of the talkLatest Issues since last Committee Report– Hardware updates

New TOFINO detectorDAQ update and performances’ improvement

– Scientific production: new papers, conferences– Current activities in data analysis

Alignment campaignSoftware improvements and new implementations New Physics Results

Preparation for the next run– Choices for the new set of targets: motivations and interests– Simulation of expected signals

Conclusions & requests for next run

33

HARDWARE UPDATES:HARDWARE UPDATES:EXPECTED GOALSEXPECTED GOALS

New TOFINO– Purpose: improve time resolution and signal/noise ratio

Improvement of a factor of 2 expected on time resolutionImprovement of an order of magnitude expected on signal/noise ratio

DAQ Update– Implementation of new modules to increase the transfer rate of

silicon detectors of a factor of 4

Other updates:– New cabling for both TOF detectors (from constant fraction

outputs to TDC’s) to reduce noise, cross-talk, attenuation, and improve rise time

– Update of TOFONE f.e. electronics

44

Hardware Update: Hardware Update: new TOFINOnew TOFINO

New TOFINO needed because of HPDs’ aging and loss of efficiencyCompletely new detector, with different spec’s

– Use of Hamamatsu photomultipliers – 1.8 mm thickness vs 2.3 mm

Thoroughly built at KEK by Japanese collaboratorsBuilding stage, as of end Apr. 05:

– Support structure : in production, to be delivered in June– Delivery in Frascati foreseen in August-September

Old TOFINO overhauled, working and ready to be used, if needed

The use of PM’s allows toThe use of PM’s allows toreduce the thickness of the reduce the thickness of the scintillator slabs (less energy scintillator slabs (less energy loss) and to suitably modify the loss) and to suitably modify the assembly geometryassembly geometry

55

NEXT DATA TAKING RATES Old data taking: L = 0.71032 8 Hz Trigger HyperNew data taking: L = 1.2 1032 14 Hz Trigger Hyper expected20 kB/event 20 Hz (Hyper + Prescaled Bhabha) = 400 kB/s

STORAGE1 fb-1 1039 cm-2s-1 / 1032 cm-2 s-1 = 107 s 400 kB/s 107 s1 fb-1 4TB (+ analysis + simulation) 10 TB

DAQ IMPROVEMENTDAQ IMPROVEMENT

Speed:– Improve VDET CRAM transfer

66 Hz → 120 Hz– Split 2 VDET VME crates into 8 parts (8 “low cost” CAEN PCI-VME

Bridges)120 Hz → 400 Hz

– Improve global event builder (4xAMD Opteron)Storage:– Upgrade Storage

1.7 TB → 10 TB (daq + offline) – Reduce Raw Data size (33 kB/ev → 20 kB/ev)

66

SCIENTIFIC PRODUCTION SCIENTIFIC PRODUCTION Nov04 - Apr05Nov04 - Apr05

Accepted Papers

Submitted Papers

Talks at International Workshops and Conferences

77

Scientific ProductionScientific Production

Accepted papers:– Evidence for a kaon bound state in K-pp produced in K- absorption at rest

Accepted for publication in Phys. Rev. Lett.Importance of the KNN, the lightest kaon-bound state beyond (1405), which is considered to be a KN system.

Submitted papers– Study of 12

ΛC production at DAΦNESubmitted to Phys. Lett. BConfirmation of observations by E369 with better resolution (1.29 MeV) and evidences for new states, even if with partial statistics and rough alignments

Talks at international conferences and Workshops:– S. Piano, @ International Workshop on “Chiral Restoration in Nuclear Medium –

Chiral05”, Riken (Japan), Feb 15-17 2005: “Strange Hadrons in Nuclei, First Results From FINUDA”

– P. Camerini, @ XLIII International Winter Meeting On Nuclear Physics, Bormio (Italy), Mar 13-20 2005: “Hypernuclear Physics with FINUDA at DAΦNE”

– T. Bressani, Report to NUPECC General Meeting, Venice Mar 18-20, 2005– L. Benussi, @ Int. Conf. On Nuclear Physics at Storage Rings STORI05, May 23-

26 2005: “Hypernuclear physics with FINUDA”

88

CURRENT ACTIVITIES IN CURRENT ACTIVITIES IN DATA ANALYSISDATA ANALYSIS

Alignments: methods and results

On the way to better understand our data…

New Physics Selected Results– Spectroscopy– Non Mesonic Weak Decays– Mesonic Decays– KNN deeply bound states

99

ALIGMENTS: procedure and methodsALIGMENTS: procedure and methods

Use of straight cosmic rays collected during and after the 2003-04 data takingIterative procedure: – First preliminary study to skim clean

events for a reliable residuals estimation

– Evaluation of I/OSIM and DCH residuals with respect to the straw tubes system

Global translational & rotational offsetsFiner tuning of single modules

– Evaluation of outer layers residuals with respect to microvertex detectors

– The two procedures should lead to equivalent results when everything is correctly aligned

Long job: good results achieved

1010

Geometry Geometry starting situationstarting situation: : global global residual distributionsresidual distributions

Straw Straw tube system takentube system takenas referenceas reference

Inner DCH: Inner DCH: ΔΔΦΦ= 180 = 180 µµm, m, ΔΔzz = 1 cm = 1 cm

Outer DCH: Outer DCH: ΔΔΦΦ= 95 = 95 µµm, m, ΔΔzz = 1.2 cm = 1.2 cm

ISIM: ISIM: ΔΔΦΦ= 90 = 90 µµm, m, ΔΔzz = 115 = 115 µµmm

OSIM: OSIM: ΔΔΦΦ= 80 = 80 µµm, m,

ΔΔzz = 177 = 177 µµmm

1111

Alignment effects on single module Alignment effects on single module geometry: fit with points on I/OSIMgeometry: fit with points on I/OSIM

Example: Example: innerinner drift chamber, cosmic fit from drift chamber, cosmic fit from vertex detectorvertex detector

Starting conditionStarting condition After After fine fine alignmentalignment

1212

A few details on residual shape improvements A few details on residual shape improvements Example: one inner Drift Chamber (I)Example: one inner Drift Chamber (I)

OLDOLD

OLDOLD

NEWNEW

NEWNEW

χχ22 distribution for the straight line fit distribution for the straight line fit(same scale!)(same scale!)

residualresidual distribution along the module distribution along the modulelongitudinal coordinate longitudinal coordinate

(sensible to rotation effects on r-(sensible to rotation effects on r-φφ plane) plane)Narrower – centered at zero!Narrower – centered at zero!

1313

A few details on residual improvements Example: A few details on residual improvements Example: one inner Drift Chamber (II)one inner Drift Chamber (II)

residualresidual distribution along the z coordinate distribution along the z coordinate Scatter plot of R residuals vs Z residualsScatter plot of R residuals vs Z residuals(sensible to rotations on z-(sensible to rotations on z-φφ plane around r) plane around r)

OLDOLD

OLDOLD

NEWNEWNEWNEW

Becomes horizontal and aligned around zero!Becomes horizontal and aligned around zero!Narrower – centered at zero!Narrower – centered at zero!

1414

After alignment: effects on physical measurementsAfter alignment: effects on physical measurementsee++ee-- (Bhabha) momenta distributions (Bhabha) momenta distributions

Bhabha events: due to the boost (12.6 MeV/c), NO monochromatic peaks for electrons and positrons must be seen

– A smeared peak centered at the same value for both is expected

– In case of disaligned geometry, the two components tend to separate in one case, and to squeeze the distribution in the second one

– Before alignment (black histos):electrons

– Presence of a double peak!– Selecting single paths, the momentum difference due to the boost

shows up clearlyPositrons

– No double peaks, but one single narrower peak (as expected)

– With alignments (red histos):Electrons

– The two peaks converge, a single peak appears, with central value µ= 0.509 MeV/c

– Resolution, without cuts: FWHM = 3.2%Positrons

– Central value µ= 0.508 MeV/c– The peak broadens, FWHM = 3.2%

With alignments the peak mean central values are better centered now for both electron and positron to the same central value (within errors), and the “raw” width for both is the same

1515

After alignment: effects on physical measurementsAfter alignment: effects on physical measurementsµµ++ spectra from different targets spectra from different targets

The central values of + momentum spectra selected per target move towards the nominal value (235.6 MeV/c – an offset is possible due to the present normalization of the mapped magnetic field)

– The spread around the central value for each target is reduced as compared with previous geometry versions (blue points)

– Lower half target set better arranged by this 1st alignment version

The total momentum spectrum, integrated over all the targets, gets the ~20% narrower

Resolution depends on cuts and on chosen road: better resolution 0.57%

0,2348

0,235

0,2352

0,2354

0,2356

0,2358

0,236

0,2362

0 2 4 6 8 10

target number

GeV

/c starting geometry

after alignments

1616

After alignment: effects on physical measurementsAfter alignment: effects on physical measurements

ππ-- spectra from the three carbon targets spectra from the three carbon targetsThe peaks corresponding to 12

C g.s. and the state at B =0 are correctly aligned, within 1 MeV/c (no severe cuts applied!), for data collected from all the three Carbon targets (one in boost direction, two in anti-boost)

Tgt 1Tgt 1

Tgt 5Tgt 5

Tgt 8Tgt 8

Raw spectra, no “spectroscopy quality cuts”Raw spectra, no “spectroscopy quality cuts”

273 MeV/c

273 MeV/c

261 MeV/c

261 MeV/c

11

5588

Tgt 1Tgt 1

Tgt 5Tgt 5

Tgt 8Tgt 8

273 MeV/c

273 MeV/c

261 MeV/c

261 MeV/c

1717

Alignment procedures: summaryAlignment procedures: summary

Many instrumental effects singled out by residual distributions study, and correctedImproved description of the geometric positioning of single modules– Macroscopic rotational and translational effects corrected– Many single-module rotational and translational effects corrected

Good improvement of real data description– Bhabha e- and e+ distributions now single-peaked and centered – µ+ momenta distributions from single target better centered

around mean value– π- peaks for hypernuclear levels from different Carbon targets

better alignedSum of peaks can now be performed

1818

Studies for data quality improvement: Studies for data quality improvement: Carbon targets (I)Carbon targets (I)

Tgt 1Tgt 1 Tgt 5Tgt 5 Tgt 8Tgt 8

Standard cuts

Standard cuts A good A good

improvement of improvement of the quality of the the quality of the signal/bck ratio is signal/bck ratio is obtained by obtained by cutting on the cutting on the distance between distance between the Kthe K- - interaction interaction vertex and the vertex and the point where the point where the ππ–– is supposed to is supposed to emerge emerge (extrapolated at (extrapolated at

the level of Kthe level of K-- stop plane)stop plane)

•Residual Residual inaccuracies in vtx inaccuracies in vtx determination determination inside targets?inside targets?

•Signals for hype Signals for hype formation in flight?formation in flight?

Boost effect on tgt 5?

Boost effect on tgt 5?

cut on vertex-extrapolated cut on vertex-extrapolated ππ distance distance

A third peak appears in between the ground state and the BA third peak appears in between the ground state and the BΛΛ = 0 MeV level = 0 MeV level

1919

Adding to the requirement on the vertices distance a further cut on

the - emission angle from the target (angle with the normal to the target plane) in-flight events should be suppressed– Sizeable reduction of the

background beyond the ground state with oblique tracks, in spite of a larger amount of target material to be crossed by the particle

– Interesting effects emerging: clean signal of a third peak

Studies for data quality improvement: Studies for data quality improvement: Carbon targets (II)Carbon targets (II)

3030oo< < <80 <80oo

Tgt 5Tgt 5

6060oo< < <80 <80oo

GeV/cGeV/c

GeV/cGeV/c

2020

Spectroscopy: Spectroscopy: 77Li targetLi targetThe 7

ΛLi hypernucleus was extensively studied with γ spectroscopy techniques, with a resolution as good as 2 keVFINUDA cannot compete with this resolution, but in spite of this the levels definition is good, especially if the presence of at least one neutral particle in the reaction (neutron!) is required

– ΔBΛ = 1.5 MeV– Compatible with 1+-3+ levels difference

(Tamura)

2 very close 2 very close peaks peaks

Requirement of at least Requirement of at least one neutral particle one neutral particle

in coincidencein coincidence

nn

2121

Spectroscopy: Aluminum targetSpectroscopy: Aluminum target

One very old (1975) measurement exists for 27

ΛAl spectroscopy

Medium-A hypernuclei production with K- at rest: ?

Closest studied hypernucleus: 28ΛSi

Attempt to adapt the 28ΛSi level

structure to a 27ΛAl excitation

spectrum 6 MeV FWHM

PRL 34(1975)683PRL 34(1975)683

2828ΛΛSiSi

KEK E140KEK E140

PRC 53(1996)1210PRC 53(1996)1210

2222

Spectroscopy: Vanadium targetSpectroscopy: Vanadium target

No measurement exists so far for 51

ΛV production in

(K-stop, π

-) reactions

First indications for the feasibility of such a reaction to produce heavy hypernuclei

#1

#6#7

#4#3#2

#5

#2:

-13.76 0.25

#3:

-10.56 0.29

#6:

-3.14 0.19

#7:

-0.70 0.20

-11.90 0.17 -10.57 0.15 -3.55 0.14 -1.55 0.11

Comparison with E369 BComparison with E369 B values (MeV) values (MeV)

Ground state missing…!Ground state missing…!

2323

Spectroscopy Results: summarySpectroscopy Results: summary

1212CC: new alignment allows to sum up spectra from all the three targets

– Increased available statistics

– Possibility to apply stricter cutsImproved definition of hypernuclear levels and background reduction

Study of finer effects possible (boost, in-flight hypernuclei production)

77LiLi: good hypernuclear levels identification

5151VV: indications for the existence of several structures already observed in (π+,K+) experiments

– Exploratory run for medium-heavy targets

– Good performance of FINUDA: first hints for the production of hypernuclei in a (K-, π-) reaction at rest even from heavy targets

Integrated Capture Rates

0

0,001

0,002

0,003

0,004

0,005

0,006

0,007

0 10 20 30 40 50 60

Mass Number AC

aptu

re R

ate/

sto

pp

ed K

-

Preliminary!Preliminary!

Hypernuclear capture rate/KHypernuclear capture rate/K--stopstop

(integrated over the bound region)(integrated over the bound region)as a function of the mass numberas a function of the mass number

5151VV2727AlAl

1212CC

77LiLi

2424

Non-mesonic weak decays: Non-mesonic weak decays: detection of neutrons with FINUDAdetection of neutrons with FINUDATOFONE’s features:– efficiency: about 10%– Resolution: 10 MeV for 80

MeV neutrons– Lower threshold: 6 MeVee

Lower detectable energy: 11 MeV

– Upper threshold: 200 MeV

Inclusive neutron energy spectrum with µ+ coincidence (no ’s from 0 decay etc.), all targets

2525

NMWD: coincidence spectra from NMWD: coincidence spectra from Carbon target: protonsCarbon target: protons

Inclusive proton spectrum, bound region

ground state region, proton spectrum

bound region, coincidence pions

Not acceptance corrected Not acceptance corrected

2626

NMWD: coincidence spectra from NMWD: coincidence spectra from Carbon target: neutronsCarbon target: neutrons

Inclusive neutron Inclusive neutron spectra in thespectra in thebound and g.s. bound and g.s. regionregion

Neutron spectra in Neutron spectra in coincidence with p, coincidence with p, in the bound regionin the bound region

Neutron spectra in Neutron spectra in coincidence with n, coincidence with n,

in the bound in the bound regionregion

2727

NMWD: total energies from NMWD: total energies from coincidence spectra: pn, nncoincidence spectra: pn, nn

Preliminary!Preliminary!

To be To be compared compared with the with the

best results best results obtained so obtained so

far for far for NMWDsNMWDs

(KEK E462-E508)(KEK E462-E508)

2828

NMWD coincidence spectra from NMWD coincidence spectra from 77Li Li targets: protons & neutronstargets: protons & neutrons

protonsprotons

neutronsneutrons

Pions (p coincidence)Pions (p coincidence)

Not acceptance corrected Not acceptance corrected

Inclusive spectraInclusive spectra

2929

Mesonic weak decays: Mesonic weak decays: first hints with FINUDAfirst hints with FINUDA

Improved pattern recognition for short tracks, using three points instead of fourHigher acceptanceHigher statisticsLower resolutionOpens the possibility to:– Study reactions with low momentum stubs– Study reactions with secondary vertices (Λ decays in

flight, Σ decays, etc)

Preliminary results, on the way to implement it fully in the reconstruction code

3030

Mesonic weak decays: coincidence Mesonic weak decays: coincidence spectra from Carbon targetsspectra from Carbon targets

Further quality cuts Further quality cuts on hypernucleus on hypernucleus

productionproduction

Selection in the Selection in the bound regionbound region

ππ-- from the mesonic from the mesonicΛΛ decaydecay

3131

Mesonic weak decays: coincidence Mesonic weak decays: coincidence spectra from spectra from 66Li targetsLi targets

ππ-- from the mesonic from the mesonicΛΛ decaydecay

Very clean peak of Very clean peak of ΛΛ in the in the

reconstructed invariant mass of reconstructed invariant mass of ππ–– and p for events in the bound and p for events in the bound

region (of region (of 5 5 ΛΛHe)He)

3232

Mesonic weak decays from Mesonic weak decays from medium-heavy targetsmedium-heavy targets

Probability of mesonic decay suppressed with mass number increase

3333

Search for kaon bound statesSearch for kaon bound states

Missing mass spectroscopy– (K-

stop,n/p) → KEK-PS E471/E549, FINUDA4He(K-

stop,n)S+(3140) → K-ppn (169 MeV bound)4He(K-

stop,p)S0(3115) → K-pnn (193 MeV bound)

Invariant mass spectroscopy– K- absorption at rest in nuclei FINUDA

K-pp →Λ+p (Λ → p+π-)

K-pn →Λ+n, Σ-+p

K-ppn → Λ+d

– Study of Λp coincidence events, with a back-to-back correlation (about 5% of the Λ events are associated with a proton)

mmΛΛ ± ± 5 MeV5 MeV

FWHM = 6 MeVFWHM = 6 MeV

3434

Improvement of KImprovement of K--pp bound state analysis with the pp bound state analysis with the new p.r. including short tracksnew p.r. including short tracks

Cos(p) < - 0.86

p

Background contributions:

The contribution of the quasi-free

reactions on two protons sits on the peak

at high invariant mass:

KK--pp pp →→ΛΛ+p+p

KK--pp pp →→ΣΣ00+p+p

3535

ππ--pppp invariant mass from invariant mass from 66Li, Li, background subtractedbackground subtracted

0p p mp+mp+mK-mp+mp+mK-

To be compared with To be compared with our first, published, our first, published, experimental result:experimental result:

The improved p.r. with the The improved p.r. with the inclusion of short tracks puts in inclusion of short tracks puts in evidence a possible decay into evidence a possible decay into ΣΣ00pp

3636

New set of targets: motivation, interests

Expected signals with the new targets’ set:

9Be, 16O

Expected improvements in the accuracy of the definition of Kpp-bound states from the lightest targets

PREPARATION FOR NEXT RUN: PREPARATION FOR NEXT RUN: SIMULATIONS, EXPECTED RATESSIMULATIONS, EXPECTED RATES

3737

New targets’ setup New targets’ setup for next data-takingfor next data-taking

Choice: 2x 6Li, 2x 7Li, 2x H2O, 2x 9Be

Target type better localization still to be studied (depending mainly on the boost and physical target features – stiffness, …)

– Lighter targets better in anti-boost direction

Thicknesses evaluation, in the hypothesis of a 1.8 mm thick TOFINO:

– 7Li, 6Li as in the previous run (+cover)– 9Be: 2 mm– H2O: 3 mm + cover (e.g. 100 µm

mylar)

First simulations of expected signals/background contributions, rough evaluation of expected rates from new targets

3838

1616ΛΛO production with FINUDA - studiesO production with FINUDA - studies

16O is a doubly magic nucleus16

ΛO production in (K-stop,π

-) reaction at rest already studied (Tamura)– Capture rate: ≤ 10-3/K-

stop

– Four levels:D: g.s. @ 279.3 MeV/c: R = 0.13x10-3

C: p(3/2)-1n,sΛ @ 272.3 MeV/c:

R = 0.30x10-3

B: p(1/2)-1n,pΛ @ 267.4 MeV/c:

R = 0.56x10-3

A: p(3/2)-1n,pΛ @ 260.4 MeV/c:

R = 1.12x10-3

First simulation of the apparatus response with:– Background reactions as in 12C:

QF Λ production

K-NN interaction with Σ±,0 conversionπ rescattering

3939

9 9 ΛΛBe production with FINUDA - studiesBe production with FINUDA - studies

Core: 8Be nucleus, highly symmetric

Production of Λ-hypernuclei with high spatial symmetry (no from 9Be, Pauli principle)– Limited data quality in (π+,K+) production

– Expected rates: some 10-4

– Observed states in (K-stop,π

-) (doublets):

g.s. @ 280+284 MeV/c: R=0.34x10-3

αα-pΛ @ 277+274 MeV/c: R=0.39x10-3

αα-sΛ @ 270-265 MeV/c: R=0.7x10-3

4040

77ΛΛLi production evaluationLi production evaluation

7ΛLi is one of the most studied

hypernuclei with γ spectroscopy– The level structure is well known– Many interesting effects still to be

studied:NMWD’sStudy of nuclear density related effectsSource for the production of neutron-rich hypernuclei

– K- + 7Li 7H + + (N/Z= 6)

Study of KNN bound states

– Measured production rate of 7ΛLi in

(K-stop, π

-) by FINUDA: ~8.5x10-4

– 8-10 times more statistics can be expected collecting 1 fb-1

NP A691(2001)123c

2 MeV FWHM LiK, 7

4141

Hyperfragments production from Hyperfragments production from 66LiLiThe 6

ΛLi hypernucleus is unstable but several hyperfragments (ΛHe, ΛH) can be produced from its decay– Study of NMWD’s– Study of rare decays– Source of neutron-rich hypernuclei

K- + 6Li 6H + + (N/Z= 5)

– Source of deeply bound KNN states

(Preliminary) capture rate value in the region of 5

ΛHe production: 6 x10-4/K-

stop

With 1 fb-1 5 times more statistics than that presently available is expected

KK-- + + 66Li Li -- + + XX– X: 5

He + p

– XX: : 44He + p + nHe + p + n44He He d + d d + d

44He He p + p + 33HH

44He He ++n++n+33HH

– XX: : 44H + p + pH + p + p44H H 44He + He + -

4242

MC simulations of KMC simulations of K--pp bound pp bound states for the next run Istates for the next run I

INPUTS: – existence of a bound K-pp state

B =115 MeV, = 67 MeV– Formation rate determined from last data taking data– Interaction in 7Li targets (typical light target)

ASSUMPTIONS:– Five times more data will be collected in the run,

(hypothesis: 1 fb-1) – Decay branching ratio : p / p = 1 / 2 – Detector efficiencies = 1– Magnetic field: B = 1 T (as in the previous data taking)

4343

MC simulations of KMC simulations of K--pp bound pp bound states for the next run IIstates for the next run II

RESULTS: – ~20 times more K-pp

events can be obtained if the integrated luminosity reaches 1 fb-1

– The mass and width of the K-pp state can be determined with much better accuracy

– The background (caused by fake neutrons) can be reduced by tagging + from K+ decays, which can be done having one order of magnitude more statistics

From the simulation:From the simulation:B = 119 ± 2 MeVB = 119 ± 2 MeVΓΓ= 60 ± 4 MeV= 60 ± 4 MeV

4444

ConclusionsConclusionsA wealth of interesting and brand new results have been extracted from the data collected in 2003-04, about – hypernuclear spectroscopy with increased statistics and better tuning– non-mesonic and (new!) mesonic decays

Measurement of first coincidence proton spectra (down to the lowest momentum ever), and (new!) neutron ones

– formation of kaon bound states– other topics already mentioned in past meetings (rare decays, neutron rich

hypernuclei, searches for hypernuclei, etc)Big effort to achieve a better apparatus alignment in order to systematically spot the drawbacks spoiling the resolutionDetailed simulations of expectations from next data taking are currently underwayHardware upgrades have been programmed in order to improve the apparatus’ performances

We just need… data! 1 fb-1 only would make us happy… and able to study a lot of new physics – By the way, at KEK the activity is quickly going on… and, of course, they

are not waiting for us!