FINUDA Status Report

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FINUDA Status Report

• 30th Scientific Committee Meeting
• LNF, 23.05.05
• A. Filippi INFN Torino

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Layout of the talk

• Latest Issues since last Committee Report
• Hardware updates
• New TOFINO detector
• DAQ update and performances improvement
• Scientific production new papers, conferences
• Current activities in data analysis
• Alignment campaign
• Software 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

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HARDWARE UPDATESEXPECTED GOALS

• New TOFINO
• Purpose improve time resolution and signal/noise
  ratio
• Improvement of a factor of 2 expected on time
  resolution
• Improvement 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 TDCs) to reduce noise,
  cross-talk, attenuation, and improve rise time
• Update of TOFONE f.e. electronics

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Hardware Update new TOFINO

• New TOFINO needed because of HPDs aging and loss
  of efficiency
• Completely new detector, with different specs
• Use of Hamamatsu photomultipliers
• 1.8 mm thickness vs 2.3 mm
• Thoroughly built at KEK by Japanese collaborators
• Building 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 PMs allows to reduce the thickness of
the scintillator slabs (less energy loss) and to
suitably modify the assembly geometry
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DAQ 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)

NEXT DATA TAKING RATES Old data taking L
0.7?1032 ? 8 Hz Trigger Hyper New data taking
L 1.2 ?1032 ? 14 Hz Trigger Hyper expected 20
kB/event ? 20 Hz (Hyper Prescaled Bhabha)
400 kB/s STORAGE 1 fb-1 ? 1039 cm-2s-1 / 1032
cm-2 s-1 107 s ? 400 kB/s ? 107 s 1 fb-1 ? 4TB
( analysis simulation) ? 10 TB
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SCIENTIFIC PRODUCTION Nov04 - Apr05

• Accepted Papers
• Submitted Papers
• Talks at International Workshops and Conferences

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Scientific 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 L(1405), which is considered to be a
  KN system.
• Submitted papers
• Study of 12?C production at DAFNE
• Submitted to Phys. Lett. B
• Confirmation 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, _at_ 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, _at_ XLIII International Winter Meeting
  On Nuclear Physics, Bormio (Italy), Mar 13-20
  2005 Hypernuclear Physics with FINUDA at DAFNE
  
• T. Bressani, Report to NUPECC General Meeting,
  Venice Mar 18-20, 2005
• L. Benussi, _at_ Int. Conf. On Nuclear Physics at
  Storage Rings STORI05, May 23-26 2005
  Hypernuclear physics with FINUDA

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CURRENT ACTIVITIES IN DATA 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

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ALIGMENTS procedure and methods

• Use of straight cosmic rays collected during and
  after the 2003-04 data taking
• Iterative 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 offsets
• Finer 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

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Geometry starting situation global residual
distributions
Inner DCH ?F 180 µm, ?z 1 cm
Outer DCH ?F 95 µm, ?z 1.2 cm
Straw tube system taken as reference
ISIM ?F 90 µm, ?z 115 µm
OSIM ?F 80 µm, ?z 177 µm
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Alignment effects on single module geometry fit
with points on I/OSIM
Example inner drift chamber, cosmic fit from
vertex detector
Starting condition
After fine alignment
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A few details on residual shape improvements
Example one inner Drift Chamber (I)
OLD
OLD
NEW
NEW
residual distribution along the
module longitudinal coordinate (sensible to
rotation effects on r-f plane)
?2 distribution for the straight line fit (same
scale!)
Narrower centered at zero!
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A few details on residual improvements Example
one inner Drift Chamber (II)
OLD
OLD
NEW
NEW
residual distribution along the z coordinate
Scatter plot of R residuals vs Z
residuals (sensible to rotations on z-f plane
around r)
Narrower centered at zero!
Becomes horizontal and aligned around zero!
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After alignment effects on physical
measurementsee- (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 clearly
• Positrons
• 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
  

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After alignment effects on physical
measurementsµ 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

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After alignment effects on physical
measurementsp- spectra from the three carbon
targets

• The 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)

261 MeV/c
273 MeV/c
Tgt 1
Tgt 5
Tgt 8
1
5
8
Raw spectra, no spectroscopy quality cuts
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Alignment procedures summary

• Many instrumental effects singled out by residual
  distributions study, and corrected
• Improved 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
• p- peaks for hypernuclear levels from different
  Carbon targets better aligned
• Sum of peaks can now be performed

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Studies for data quality improvement Carbon
targets (I)
Tgt 1
Tgt 5
Tgt 8

• A good improvement of the quality of the
  signal/bck ratio is obtained by cutting on the
  distance between the K- interaction vertex and
  the point where the p is supposed to emerge
  (extrapolated at the level of K- stop plane)
• Residual inaccuracies in vtx determination inside
  targets?
• Signals for hype formation in flight?

Standard cuts
Boost effect on tgt 5?
cut on vertex-extrapolated p distance
A third peak appears in between the ground state
and the B? 0 MeV level
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Studies for data quality improvement Carbon
targets (II)
30o

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

GeV/c
Tgt 5
60o
GeV/c
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Spectroscopy 7Li target

• The 7?Li hypernucleus was extensively studied
  with ? spectroscopy techniques, with a resolution
  as good as 2 keV
• FINUDA 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
• ?B? 1.5 MeV
• Compatible with 1-3 levels difference (Tamura)

Requirement of at least one neutral particle in
coincidence
2 very close peaks
n
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Spectroscopy Aluminum target

• One very old (1975) measurement exists for 27?Al
  spectroscopy
• Medium-A hypernuclei production with K- at rest
  ?
• Closest studied hypernucleus 28?Si
• Attempt to adapt the 28?Si level structure to a
  27?Al excitation spectrum

PRL 34(1975)683
6 MeV FWHM
PRC 53(1996)1210
28?Si KEK E140
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Spectroscopy Vanadium target

• No measurement exists so far for 51?V production
  in (K-stop, p-) reactions
• First indications for the feasibility of such a
  reaction to produce heavy hypernuclei

Comparison with E369 B? values (MeV)
Ground state missing!
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Spectroscopy Results summary

• 12C new alignment allows to sum up spectra from
  all the three targets
• Increased available statistics
• Possibility to apply stricter cuts
• Improved definition of hypernuclear levels and
  background reduction
• Study of finer effects possible (boost, in-flight
  hypernuclei production)
• 7Li good hypernuclear levels identification
• 51V indications for the existence of several
  structures already observed in (p,K)
  experiments
• Exploratory run for medium-heavy targets
• Good performance of FINUDA first hints for the
  production of hypernuclei in a (K-, p-) reaction
  at rest even from heavy targets

Preliminary!
12C
27Al
51V
7Li
Hypernuclear capture rate/K-stop (integrated
over the bound region) as a function of the mass
number
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Non-mesonic weak decays detection of neutrons
with FINUDA

• TOFONEs 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

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NMWD coincidence spectra from Carbon target
protons

• Inclusive proton spectrum, bound region

ground state region, proton spectrum
Not acceptance corrected
bound region, coincidence pions
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NMWD coincidence spectra from Carbon target
neutrons
Inclusive neutron spectra in the bound and g.s.
region
Neutron spectra in coincidence with p, in the
bound region
Neutron spectra in coincidence with n, in the
bound region
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NMWD total energies from coincidence spectra
pn, nn
To be compared with the best results obtained
so far for NMWDs (KEK E462-E508)
Preliminary!
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NMWD coincidence spectra from 7Li targets
protons neutrons
Inclusive spectra
Not acceptance corrected
protons
Pions (p coincidence)
neutrons
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Mesonic weak decays first hints with FINUDA

• Improved pattern recognition for short tracks,
  using three points instead of four
• Higher acceptance
• Higher statistics
• Lower resolution
• Opens the possibility to
• Study reactions with low momentum stubs
• Study reactions with secondary vertices (? decays
  in flight, S decays, etc)
• Preliminary results, on the way to implement it
  fully in the reconstruction code

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Mesonic weak decays coincidence spectra from
Carbon targets
p- from the mesonic ? decay
Further quality cuts on hypernucleus production
Selection in the bound region
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Mesonic weak decays coincidence spectra from 6Li
targets
p- from the mesonic ? decay
Very clean peak of ? in the reconstructed
invariant mass of p and p for events in the
bound region (of 5 ?He)
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Mesonic weak decays from medium-heavy targets

• Probability of mesonic decay suppressed with mass
  number increase

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Search for kaon bound states

• Missing mass spectroscopy
• (K-stop,n/p) ? KEK-PS E471/E549, FINUDA
• 4He(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 ??p (? ? pp-)
• K-pn ??n, S-p
• K-ppn ? ?d
• Study of ?p coincidence events,
  with a back-to-back correlation
  (about 5 of the ? events are
  associated with a proton)

FWHM 6 MeV
m? 5 MeV
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Improvement of K-pp bound state analysis with the
new p.r. including short tracks
K-pp ??p
Background contributions The contribution of
the quasi-free reactions on two protons sits on
the peak at high invariant mass
K-pp ?S0p
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p-pp invariant mass from 6Li, background
subtracted
To be compared with our first, published,
experimental result
S0p
Lp
mpmpmK-
The improved p.r. with the inclusion of short
tracks puts in evidence a possible decay into S0p
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PREPARATION FOR NEXT RUN SIMULATIONS, EXPECTED
RATES

• 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

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New targets setup for 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

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16?O production with FINUDA - studies

• 16O is a doubly magic nucleus
• 16?O production in (K-stop,p-) reaction at rest
  already studied (Tamura)
• Capture rate 10-3/K-stop
• Four levels
• D g.s. _at_ 279.3 MeV/c R 0.13x10-3
• C p(3/2)-1n,s? _at_ 272.3 MeV/c R
  0.30x10-3
• B p(1/2)-1n,p? _at_ 267.4 MeV/c R
  0.56x10-3
• A p(3/2)-1n,p? _at_ 260.4 MeV/c R
  1.12x10-3
• First simulation of the apparatus response with
• Background reactions as in 12C
• QF ? production
• K-NN interaction with S,0 conversion
• p rescattering

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9 ?Be production with FINUDA - studies

• Core 8Be nucleus, highly symmetric
• Production of ?-hypernuclei with high spatial
  symmetry (no from 9Be, Pauli principle)
• Limited data quality in (p,K) production
• Expected rates some 10-4
• Observed states in (K-stop,p-) (doublets)
• g.s. _at_ 280284 MeV/c R0.34x10-3
• aa-p? _at_ 277274 MeV/c R0.39x10-3
• aa-s? _at_ 270-265 MeV/c R0.7x10-3

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7?Li production evaluation

• 7?Li is one of the most studied hypernuclei with
  ? spectroscopy
• The level structure is well known
• Many interesting effects still to be studied
• NMWDs
• Study of nuclear density related effects
• Source for the production of neutron-rich
  hypernuclei
• K- 7Li ? 7LH p (N/Z 6)
• Study of KNN bound states
• Measured production rate of 7?Li in
  (K-stop, p-) by FINUDA 8.5x10-4
• 8-10 times more statistics can be expected
  collecting 1 fb-1

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Hyperfragments production from 6Li

• The 6?Li hypernucleus is unstable but several
  hyperfragments (?He, ?H) can be produced from its
  decay
• Study of NMWDs
• Study of rare decays
• Source of neutron-rich hypernuclei
• K- 6Li ? 6LH p (N/Z 5)
• Source of deeply bound KNN states
• (Preliminary) capture rate value in the region of
  5?He production 6 x10-4/K-stop
• With 1 fb-1 5 times more statistics than that
  presently available is expected

• K- 6Li ? ?- X
• X 5?He p
• X 4?He p n
• 4?He ? d d
• 4?He ? p 3H
• 4?He ? ?n3H
• X 4?H p p
• 4?H ? 4He ?-

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

• INPUTS
• existence of a bound K-pp state
• B 115 MeV, G 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 Lp / S0p 1 / 2
• Detector efficiencies 1
• Magnetic field B 1 T (as in the previous data
  taking)

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MC simulations of K-pp bound states 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 m from K decays, which can
  be done having one order of magnitude more
  statistics

From the simulation B 119 2 MeV G 60 4 MeV
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Conclusions

• A 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 resolution
• Detailed simulations of expectations from next
  data taking are currently underway
• Hardware 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!