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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!