Gianfranca De Rosa

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CHARM IN EMULSION

• Gianfranca De Rosa
• University of Naples

DPF2002, Williamsburg May 24-28
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Neutrino charm production
?-
?
??
?,ho
Vcd2,Vcs2
Charm fragmentation D0 D Ds ?c z pc/pD
?,e,h
d,s
c
Ehad
Quark density functions, strange sea (?)
NLO effects
radiative gluon and self energy diagrams
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Charm production by n interactions
CDHS (CERN WBB)
Zeitschr. Phys. C (1982) 19-31
9922 ?-? , 2123 ??- events
CCFR (NuTeV)
Zeitschr. Phys. C (1995) 189-198
5044 ?-? , 1062 ??- events
CHARMII (CERN WANF)
Eur. Phys. J., C11 (1999) 19-34
4111 ?-? , 871 ??- events
NOMAD (CERN WANF)
CERN EP 2000-072, submitted to Phys.Lett.B
2714 ?-? , 115 ??- events
CHORUS (CERN WANF)
535 charm events in emulsion
E531 (Fermilab, Nagoya)
122 charm events in emulsion only measurement of
D0 D Ds ?c B(c??) crucial for other
experiments
Phys. Lett. B 206 (1988) 375-379
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CHORUS experiment(CERN Hybrid Oscillation
Research ApparatUS)

• nt appearance in a pure nm beam
• nm energy well above t production threshold (
  ltEgt27 GeV)
• A target/detector of nuclear emulsions allows
  direct observation of t decay
• 770 Kg of nuclear emulsions divided in 4 stacks
  perpendicular to the beam
• Very high spatial resolution (1µm) with 300
  tridimensional hits/mm
• Suitable to detect the t decay signature
• Interaction vertex
• Short t path 1 mm (ct 87 µm)
• kink as decay topology

Suitable also for charm Phisycs !
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CHORUS detector
-
-
m
m


Calorimeter
-
-
h
h
Muon

Muon

spectrometer
spectrometer

Air core

Air core
spectrometer and
spectrometer and
emulsion tracker
emulsion tracker
Veto plane
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Target region

• Fiber target tracker (TT)
• angle resolution 2 mrad
• position resolution 150 mm

• Emulsion target
• 4 stacks each made of 36 plates
• Total mass 770 kg

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CHORUS emulsions
MIP 30 ? 40 grains / 100 ?m transverse
resolution 0.5 ?m depth of focus 1 to 3 ?m
Nucl. Instr. Meth. A 447 (2000) 361-376
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Procedure of analysis

• Event reconstruction by electronic detectors

predictions for the event location in the
emulsion target

• vertex location

Automatic emulsion scanning follow-up the
selected tracks until interaction vertex

• decay search

Full event reconstruction in the vertex region by
a new scanning technique Offline selection for
decay topology search Computer assisted eye-check
to confirm presence of decay

• post-scanning analysis

Daughters momentum reconstruction
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Emulsion data acquisition

• CCD image
• 120150 µm
• Focal depth
• 3 µm

The most upstream 100 µm of each plate are scanned
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Netscan tecnique
scanning speed
All tracks (qlt400mrad) in the scanning volume
(1.5X1.5X6.3mm3) are recorded at 11 min./event.
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Netscan tecnique

• All located events are netscanned
• Pick up all track segments in an 8-plates deep
  fiducial volume around vertex
• ? Decay search
• Offline analysis of emulsion data
• track and vertex fitting (MCS)

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Charm selection

• matching to electronic detectors
• secondary vertex with at least one or more
  matched tracks OR
• isolated, matched track with large impact
  parameter

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Manual checks

• Sample of 25,693 nm CC interactions, 15 of
  final statistics
• 851 (3.3) selected events

• Neutral 33

V4 57
V2 226

• Charged 30

C1 121
C3 124
C5 7

• Backgr 37

2ry int. 68
e e-, ? ray 44
low p 204
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D0 production rate
s (D0) / s (CC) 1.99 ? 0.13 (stat.) ? 0.11
(syst.)
D0 ? V4 / D0 ? V2 23.1 ? 4.0
s(D0)/ s(CC)
s (D0) / s(charm) 53 ? 11
Using the NOMAD results on total charm production
and on muonic branching of charmed particle
Slow rescaling model mc 1.3 GeV/c2
Phys.Lett.B 527 (Measurement of D0 production in
, A.Kayis-Topaksu et al.)
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Associated charm production
pb 500 MeV/c dE/dx proton P
0.78 GeV/c P gt 330 MeV/c
180 - 110
transverse plane
1ry vertex Ns 2, Nb 6
1st kink
D0 f.l. 340 mm
2st kink
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Semi-muonic branching ratio
Basic idea High purity selection to use
automatic reconstruction

• special MCS treatement in track and vertex fit
• 1/4 of total statistics checked by eyes to check
  the selection purity

Candidate events for charm production 1055
90.61.9 selection purity
956 ? 35
Selected events with 2ry muons
88 ? 10 (stat) ? 8 (syst)
Result
B? 9.3 ? 0.9 (stat) ? 0.9 (syst)
only direct measurement in agreement with other
experiments
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Quasi-elastic charm production
So far only 3 events observed in emulsion
(E531)
a) ?? n ? ?- ?c b) ?? n ? ?- ?c
(?c) c) ?? p ? ?- ?c(?c)
dedicate charm selection
54 qe-charm topologies

• tracks with large minimum distance from muon
• cut on track multplicity at primary vtx
• cut on hadronic energy

C1 24
C3 29
C5 1
QE rate will be measured
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Outlook

• D0 production rate

Data taking ongoing 300 D0 ? 2000 D0

• Inclusive charm, including charged

4,000 neutrino-induced charm events
Fragmentation fractions D0 D Ds ?c
B(c??), Vcd, s(x),...

• Associated charm production both in NC and CC

Background evaluation based on CHORUS data and
FLUKA Improved selection efficiency 1 ? 25

• Exclusive channels

Proton identification MCS momentum measurement ??
detection
?c absolute BR, QE ?c production

• Antineutrino charm production

20 ? 300 nm charm events
so far no n data in emulsion