Emulsion chambers

1
Emulsion chambers UHE families

• A.S.Borisov
• P.N.Lebedev Physical Institute, Russian Academy
  of Sciences,
• Moscow, Russia

2
Contents

• 1. Introduction. Historydevelopment.
• 2. CR researches with XREC.
• 3. Main results of EC experiments.
• 3. Unusual events in cosmic rays.
• 3. What we need for their explanation?
• 4. What can QGP give?
• 5. Predictions for CR energy spectrum
• 6. Conclusions

3
Introduction

• Emulsion chamber technique is one of the most
  elaborated one in CRparticle physics with long
  history

4
Bright history of photographic/emulsion technique
in CRparticle physics.

• Henri Becquerels discovery (1896) of natural
  radioactivity by observing the blackening of
  photographic paper with uranium salts
• in 1937 two Viennese physicists, Marietta Blau
  and Herta Wambacher, had exposed photographic
  emulsions for five months at 2,300 m in the
  Austrian Alps and had seen the tracks of low
  energy protons as well as 'stars' or nuclear
  disintegrations probably caused by CRs

5
Bright history of photographic/emulsion technique
in CRparticle physics.

• . . .
• charged pion discovery at Bristol by Lattes,
  Muirhead, Occhialini and Powell (1947) with
  newly developed high sensitivity boron-loaded
  photographic (nuclear) emulsions exposed to CRs
  at Pic-du-Midi in the Pyrenees (2,867 m a.s.l.)
  they observed multiple scattering of a meson
  followed by its nuclear capture in the emulsion
  and producing a nuclear disintegration as well as
  two-body decay p?mnm due to Lattes proposal
  new searches for double meson events were moved
  in 1947 to Mt.Chacaltaya (5600 m a.s.l.)

6
Complete p?m?e decays in nuclear emulsions
showing the constancy of the muon range
Type of emulsion detector Ilford nuclear
research emulsions 50 mm thick while Muon range
was 600 mm (2D detector)
7
Nuclear emulsion plates

• provides tracks of ionization produced by a
  charged particle due to disintegration of AgBr
  microcrystals (grains) suspended in gelatin
• measurements and particle identification
• - particle range RR(E)
• - multiple scattering angle ?K/pbc1/E
• - grain density g v.s. ? ? m
• - measurement of the charge is based on the
• ionization energy loss dE/dxZ2/b2
• - track density of d-electrons nen(E)

8
Emulsion technique advantages

• simplicity of operation
• versatility
• comparatively low weight
• continuous sensitivity
• high efficiency for particle distinguishing
• high spatial resolution (1 mm)
• direct visual image of event

9
History of EC technique and its development. Main
milestones.

• . . .
• In 1948, observations with nuclear emulsions,
  exposed at high-altitude balloons, by research
  groups from the University of Minnesota (Ney,
  Lofgren, Oppenheimer) and the University of
  Rochester (Bradt, Peters) showed that the primary
  cosmic particles are mostly protons with some
  helium nuclei (alpha particles) and a small
  fraction heavier nuclei (up to Fe)
• 1950 - 1960-ies wide use of emulsion technique
  in both CR and accelerator experiments. Further
  developments (emulsion plate stacks - 3D
  detectors, emulsion chambers, etc.)

10

• . . .
• Emulsion Chamber (EC) consists of a sandwich
  structure made of thick metal plates (passive
  material) and thin emulsion layers (tracking
  device). Most of the detector mass consists of
  metal plates, allowing for a substantial cost
  reduction (1/100) compared with stacks of pure
  emulsions and allowing to reach higher detector
  masses. In addition, the EC allows the
  identification of particles and the measurement
  of their kinematical parameter by observing in
  detail specific ionization, showering and
  multiple Coulomb scattering.
• EC combines features of a calorimeter and a high
  resolution tracking detector.

11
History of EC technique and its development.
Main milestones.

• . . .
• In 1971, K. Niu of Nagoya University observed
  X-particles (open-charm) in CR with emulsions
  three years prior to the discovery of the hidden
  charm particle, J/?, at CERN and Fermilab
• In1977, hadro-produced B B pair event observed
  in nuclear emulsions by WA75 at CERN, using a p-
  beam of 350 GeV.
• In 2000, the DONUT experiment at Fermilab allowed
  the first direct observation of tau-neutrino.

12
CR studies with XREC

• XRECs use a specific type of emulsions, i.e.,
  X-ray films as more cheep sensitive materials
  enabling to simplify the measuring procedure.
  XREC technique, combining features of that of a
  calorimeter and a high resolution tracking
  detector, makes it possible to assemble
  large-scale (1000 m2) detectors at mountain
  altitudes and thus to move CR researches to
  energy region E0 1015 1017 eV where direct
  measurements in stratosphere or in outer space
  are practically impossible due to low PCR flux
• I (E0 1016 ) 1 particle/m2/sr/year

13
Main principles and scheme of XREC experiments at
mountain elevations

• XRECs detect highest energy (g,e/- ) and charged
  hadrons within EAS cores initiated by the PCR
  particles in the thick air target above the
  chamber
• The higher the altitude, the weaker is the
  shielding effect of the atmosphere and the higher
  is the sensitivity of observed events to the PCR
  particle origin and its initial interactions
  thanks to less number of nuclear interactions
  contributing to the events being recorded.

14
XREC technique. Some details.

• XREC, made of a sandwich of various material
  plates such as lead or iron interleaved with
  X-Ray films, is a passive tracking coordinate
  detector which enables experimentalists to
  measure track geometry parameters of high energy
  particles
• Dx, Dy 50 mm, Dq 3?, Dj 15?
• High energy electromagnetic particles (Eth 2-4
  TeV) induce shower cascades in lead/iron which
  produce darkness spots on films placed deep in
  the absorber. Optical density DR of a spot within
  diaphragm of radius R measured with a
  microphotometer DR DR(E,t), where t is the
  depth of observation in absorber in radiation
  lengths. Energy determination accuracy
• sE/E0.2-0.3

15
XREC technique and conclusions

• Physical conclusions from XREC experiments, i.e.,
  on characteristics of hadron interactions as well
  as PCR mass composition and energy spectrum, are
  derived from comparison of experimental results
  with those of simulations calculated in various
  models of nuclear and strong interactions under
  assumption of different PCR mass composition and
  spectrum shape and accounting for the chamber
  response.
• Detailed simulations revealed higher sensitivity
  of observables in XREC experiments to parameters
  of strong interaction models and mass composition
  as compared to EAS experiments due to less
  number of successive interactions contributing to
  an event.
• Due to the high energy threshold (Eth 4 TeV),
  XREC experiments study production of the most
  forward particles, i.e., they study the kinematic
  fragmentation region of a projectile particle
  XREC experiments should be considered as
  complementary ones to colllider experiments.

16
Calibration of XREC technique

• The method of energy determination by XREC has
  been calibrated in accelerator beams of electrons
  and pions and proved in the fixed target
  experiment on reconstruction of p0 mass in the
  decay p0 ?2g by means of measuring of energy of
  two initial g-rays and opening angle F

• Calibration of XREC technique with nuclear
  emulsions.
• Mutual calibration of XREC technique applied in
  Pamir and Chacaltaya experiments.

17
Mutual calibration of XREC technique applied in
Pamir and Chacaltaya experiments

• Joint Soviet- Japanese experiment
• Notations
• R(EP-ECh)/ (EPECh)
• Dashed (blakened) area is for (EPECh)/ 2 15
  TeV

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Simulation of XREC response

• Simulation of XREC response with GEANT and
  similar original programs allowing for detailed
  structure of XREC calorimeters.
• Simulation of XREC technique accounting for
  overlapping of neighboring showers and finite
  spatial resolution and recognition ability.
• Simulation of measuring procedure.

19
Simulation of XREC response with GEANTGHEISHA
Notations S Efall incident (genious) family
energy S Ereley measured (observed)
energy
20
CR studies with XREC

• Mt.Chacaltaya EC experiment started by
  Brazil-Japan collaboration in 1962 operated EC
  which contained simultaniously nuclear emulsions
  and X-Ray films (5200 m a.s.l., 560 g/cm2)
• Aircraft-borne experiment with XREC by Smorodin
  et al. (conducted in 1965-1968)
• Mt.Fuji EC, started in 1968, exposed thick-type
  lead EC (3750 m a.s.l., 650 g/cm2 )
• Pamir experiment, launched in 1971-1973, exposed
  the largest XREC (4370 m a.s.l., 595 g/cm2 )
• Mt.Kanbala (5500 m) XREC experiment conducted by
  Japan-China collaboration in 1981-1993 with
  thick-type iron EC.

21
Chacaltaya two-storey chamber(5200m a.s.l.,
Bolivia)
Calibration of XREC technique with emulsions
22
Pamir experiment
Observables n?,h, E?,h, ?E?,h, x, y, R?,h? and
various combinations

• A family definition and selection criteria
• a collimated (Dq?3?, Dj?15?) bundle of particles
  originated from one PCR particle
• ?E? ? 100 TeV, n? ? 3, E? ? Eth 4 TeV, Eh(?) ?
  Eth, R?,h?? 15 cm
• Total exposition ST 4000 m2yr
• Available statistics Nf ? 2000

23
The Pamir-Chacaltaya experimental results

• Since 1980, the members of the Pamir
  collaboration worked side by side with physicists
  engaged in the Mt.Chacaltaya Experiment in the
  framework of the Pamir-Chacaltaya Joint EC
  Experiment and carried out several joint
  expositions both at the Pamirs and Mt.Chacaltaya
  the results of which were analyzed in numerous
  joint papers

• In the energy range E051014 31015 eV which
  corresponds to released energies ?E? 100 400
  TeV, QGS model-inspired simulation codes (MC0,
  MQ, etc.) incorporating hard jet production and
  based on extrapolation of accelerator data
  produce a good fit to the main experimental
  results
• estimation of the inelastic cross-section for
  p14N interactions gave a value of 360 ? 40 mb
• increase of the inelasticity coefficient K for
  p14N reactions from K0.5 at accelerator energies
  up to K 0.78 at E0?1016 eV

24
The Pamir-Chacaltaya experimental results

• scaling violation in the fragmentation region for
  pion production was established, i.e., the
  inclusive cross-section falls 2-3 times at x
  0.3, when the energy increases from that
  attainable with accelerators, due to
  re-scattering of particles from nucleons inside a
  nucleus
• estimation of transversal cross-section for
  quark-gluon string production ?jet (24 ? 7) mb
  at jet transverse momentum ptjet ? 3 GeV/c and
  XjF gt 0.05
• existence of the Landau-Pomeranchuk-Migdal effect
  was confirmed.
• Still, even in the low energy range E051014
  31015 eV experimental data exhibit larger
  fluctuations than simulated ones which can be
  account for by under estimation of chamber
  response only partially (Centauro events,
  penetrating particles, etc).

25
Unusual events
In the energy range 41015-1017 eV
significant discre-pancies between experimental
and simulated data are observed. The most
challenging phenomena are

• a high intensity of multi-core halo events
• the coplanar emission of the most energetic
  hadrons and g-rays in the multiple particle
  production
• Centauro events with abnormal ratio of charged to
  neutral particles
• abnormal behavior of a hadron absorption curve,
  which significantly deviates from exponential law
  at large depth in lead absorber.

26
Halo events

• If E0 1016 eV, a sufficiently high number of
  overlapping under-the-threshold EPhC may overlap
  creating an optical halo, i.e., a large diffuse
  optical spot inside the corresponding g-family
  with a visible energy ?E? ? 500 TeV. Sometimes
  area of a halo S cm2 The fraction of halo
  events increases with family energy and, at
  ?E??1000 TeV, amounts up to 70 .

Scanner image of FIANIT halo event
SD0.5 1017 mm2 visible energy E (23)?1016
eV (Isodence D0.5 corresponds to particle
density 0.04 mm-2)
Halo event selection criteria ?E? ? 500 TeV, n?
? 3, E? ? 4 TeV, SD0.5 ? 4 mm2 or ?Si D0.5 ? 4
mm2, Si D0.5 ? 1 mm2 R? ?? 15 cm Statistics
NH 61, ST3000 m2?year Nf tot (?E? ??
500 TeV) 143
27
Simulation of Halo events

• MC0 is a QGS-model which
• satisfactory reproduces the main characteristics
  ofg-families with ?E? 100400 TeV
• describe well the halo size spectrum of
  g-families with ?E? ? 500 TeV
• Assumed PCR mass composition

28
Simulation of Halo events
Energy spectra of protonsaccording KASCADE and
Tibet data
Contribution of primary particlesfrom different
energy intervalsto intensity of halo
gamma-families
All particles
protons
Pamir
Fraction of halo g-families with ?E? ? 500 TeV
produced by different PCR nuclei
29
Conclusions based on halo g-family intensities

• Proton fraction in the PCR mass composition at
  E0 ?? 1016 eV is not less then 15.
• The results of the Pamir experiment contradict
  to claims for drastic vanishing of protons and
  ?-particles at energies around 1016 eV.
• Significant increasing of proton fraction in the
  PCR at energies ? 1017 eV is not enough to agree
  experimental data with the simulations.

30
Phenomenon of coplanar emission of hadrons

• The effect, first observed in the Pamir
  experiment, manifested itself as a strong
  tendency for tracks of the most energetic
  particles in ?-h families as well for their
  narrow bundles (family cores) to be aligned along
  a certain straight line in the target plane .
• The highest energetic cores (HEC) in a family can
  be represented by
• halo cores
• ?-clusters or reconstructed ?0
• single gamma-ray or hadron.

An example of aligned 3-core halo event
31

• For quantitative definition of events with N
  cores aligned along one straight line, the
  following criterion was introduced

where ?ijk is the angle between the straight
lines connecting the i-th and j-th cores with the
k-th core.
The parameter ?N 1 in the case of complete
alignment of N cores along one straight line and
tends to -1/(N-1) in an isotropic distribution
case.
Families containing N-core structures, composed
of the HEC and characterized by ?N ? ?C 0.8 are
referred to as aligned events.
32
Aligned g-families
Example of the target diagram of an aligned
superfamily. Circles schematically show particles
unified into clusters.
l4-distribution of experimental and simulated
g-families in two energy ranges after applying of
clusterization procedure
33
At ?E? ? 700 TeV the fraction of the events with
?4 ? 0.8FhEXP(l4gt0.8) 0.26?0.09for
C-chambersFhEXP(l4gt0.8) 0.43?0.17for
Pb-chambers
Nalign/Ntotal,
?E?, TeV Dependence of the fraction of families
with alignment on ?E? Experiment Pb-chamber
data, C-chamber of the Pamir Joint
Experiment, Pamir C-chamber Simulations simul
ated families with MC0-model randomly incident
objects
34
Electromagnetic clustering procedure for gs and
p0 reconstruction
1.2 TeVcm for gammas 3.4 TeVcm neutral
pions
Dependence of aligned event fraction F(?4c gt 0.8)
and efficiency for p0 reconstruction on
decascading parameter zc.
Simulated family dissection efficiency of p0
reconstruction is the highest at zc3.6 TeV cm,
i.e. ltPgtltEgt0.8860.03 almost 90 where P
ncp / nc - purity of extracted electromagnetic
clusters E ncp/ ncp - efficiency
of gathering of all e-m particles ncp related to
a given p0
into a single cluster nc total
number of particles in a cluster ncp-
number of particles in a cluster originated from
p0 dominating in the
extracted cluster

35
Dependence of primary cosmic ray particle
energy E0 and fraction F(?4c gt 0.8) of
? -families with aligned four highest energy
neutral pions on total number Np0 of
extracted pions with Ec gt 10 TeV.
36
Main treats of coplanar production of hadrons in
the most forward region

• existence of an energy threshold for aligned
  event production (?E? 700 TeV ? E0 ??
  (58)1015 eV)
• related to most energetic particles
• large transverse momentum (about several GeV/c)
• A ratio of longitudinal component ltptgt of the
  average transverse momentum of secondaries to
  transverse component ltptgt-, determined in
  reference to the coplanarity plane, can be
  estimated as ltptgt/ltptgt- ltRcgt4/ltRcgt4-12?3
• considerable cross-section for the production
  (spcopl spinel).

37
Aligned events in Stratosphere
Two superfamilies induced by the PCR particles
with E0 ?? 81015 eV were once detected at the
balloon and aircraft-borne EC experiments by
chance and both of them appeared to be extremely
aligned
38
Aligned events in Stratosphere
Estimation of production heights Hprod above the
chamber by various methods (triangulation,
invariant mass distributions, etc.)
39
Strana
Baloon-borne experiment carried out by Prof.
Dobrotin and his colleagues of Lebedev Physical
Institute in 1975
Estimated primary energy E0 ? 21016 eV
40
JF2af2 (Concorde)

• Xray film under 8 c.u.

• Lego plot with the 4 most energetic Gamma s

34 g s are aligned (about 50 of the visible
energy) 3 most energetic clusters (A,AP,B) each
containing the highest energy gammas (about 33
of the visible energy) are aligned
41
Penetrating hadrons with abnormal absorption

• In the range of 0?70 rad. lengths, the absorption
  curve obeys the standard exponential law with
  index ?1(200?5) g/cm2. However, at larger depths
  (gt70 c.u.), the absorption length of had-rons in
  lead changes and becomes as high as ?2(340?80)
  g/cm2.
• This unusual phenomenon seems to be similar to
  that discovered earlier at the Tien Shan Mountain
  Station when absorption of EAS hadron cores in a
  hadron calorimeter was studied (a hypothesis of
  long-flying component of cosmic rays introduced
  by V.I.Yakovlev).

dN/dt, m-2
t, c.u.
Distribution of the cascade origin points for
hadrons with Eh(?)? 6.3 TeV obtained in the
Pamir experiment by means of homogeneous
Pb-chambers 110 cm thick.
42
RHIC experiments (STAR, PHENIX)
STAR 1,4?0,2?0,4 mb PHENIX
0,92?0,15?0,54 mb
43
Testing of the charmed origin of penetrating
particles
Hypothesis Excessive cascades are initiated by
charm particles (
?2 mb/nucleon )
44
Two-storeyed X-ray emulsion chamber with air gap
A section view of ionization-neutron calorimeter
with 2-storied X-ray emulsion chamber at the
top of it.
45
Upper storey of XREC with 2.2 m air gap at Tien
Shan
46
Lower storey of XREC with 2.2 m air gap at Tien
Shan
47
Centauro-type events

• Centauro events first observed by the
  Japan-Brazil Collaboration in a two-storied
  emulsion chamber exposed at the Mt.Chacaltaya
  are distinguished by abnormally high fraction of
  energy carried by charged hadrons as compared to
  that of gammas.

The Pamir experiment 88 ?-h families were
analysed with visible energy SEg?Eh(?)? 100 TeV
which were detected by Pb-chambers of 60 cm thick
with total exposition 132 m2?year.
Nh vs. Qh?Eh(?)/(SEg?Eh(?)) (Dots stand for
experimental events while crosses refer to
simulated ones. Candidates for Centauro-type
events in the Pamir and the Chacal-taya
experiment data are marked by squares and
circles, respectively).
48
CENTAURO original data and interpretation
Nh100, lt pt gt 1.5 GeV/c , non-p0 production
49
(No Transcript)
50
re-analysis
Shower-cluster in S55 is not an upper body of
that in I12 !!
51
gap-passing atmospheric family ??
52
atmospheric jet produced at 50m above the chamber
?
V.V.Kopenkin et al. PRD68(2003) 052007
impossible !!
53
C-jet with very large pt and multiplicity ?
no geometrical convergence to target layer !!
54
again very exotic !!
a bundle of hadrons w/o accompanying g-rays
no collisions in the upper chamber !!
28 collisions In the target layer !!
55
CONCLUSIONS

• Several new phenomena are observed in CRs with
  XREC at energies around and beyond the knee
  energy which are hard to explain within SM.
• All unusual events and phenomena observed in EC
  experiments can be accounted for by an assumption
  of presence of highly penetrating particles in
  CRs which are able to penetrate deep in the
  atmosphere and then interact (or decay) nearby
  XREC producing halo events, coplanar events or
  Centauro-type events.

56
Thank you for attention !
57
Hybrid (combined) experiments

• Mt.Norikura (2770m a.s.l., 740 g/cm2), started
  since 1958, ECAir Shower array
• Hadron experiment at Tien Shan
• SYS at Mt.Chacaltaya Chacaltaya EAS array of
  Saitama-Yamanashi-San Andres universities
• 5200m a.s.l., 550 g/cm2, from 1977
• Hadron-M experiment within ATHLET project at Tien
  Shan
• MAKET detector within ANI experiment (1985-89)
• Since 1996, a hybrid experiment consisting of
  emulsion chambers, burst detectors and the
  Tibet-II air-shower array was carried out at
  Yangbajing (4300 m a.s.l., 606 g/cm2) in Tibet
  (3-year operation)

58

• Development of emulsion technique and new
  experiments
• Hybrid (combined) CR experiments (Hadron, Tibet,
  SYS)
• OPERA experiment Emulsion cloud chambers
• accelerator experiments with hybrid detectors
  where nuclear emulsions are combined with
  electronic detectors and profit is taken of the
  remarkable technological progress in automated
  analysis (CHORUS, etc.)

59
OPERA Experiment

• OPERA is a long-baseline neutrino oscillation
  experiment designed to perform a nt appearance
  search in the nm beam from CERN to Gran Sasso
  underground laboratory, 730 km from CERN
• Identification of the t lepton produced by a nt
  CC interaction is based on the use the Emulsion
  Cloud Chamber (ECC) which consists of a modular
  structure made of a sandwich of passive material
  plates (Fe, Pb) interleaved with emulsion films.
  The emulsion is used only for tracking and t
  decays are identified by a direct kink detection
• Algorithm of electron shower reconstruction
  developed in OPERA makes it possible to obtain a
  nice e/p separation and good shower energy
  estimation (dE0.1-0.2).

60
OPERA Experiment
Detection of t leptons Sensitivity to Dm2
1.6-4.0 x 10-3 eV2 High background rejection and
Mtarget O(1 kton)
61
YBJ hybrid experiment
62
YBJ hybrid experiment

• Tibet-II air shower array consisted of 697
  scintillation counters which are placed at a
  lattice with 7.5 m spacing and 36 scintillation
  counters which are placed at a lattice with 15 m
  spacing. Each counter has a plate of plastic
  scintillator, 0.5 m2 in area and 3 cm in
  thickness, equipped with a 2-inch-in-diameter
  photomultiplier tube (PMT).
• At the center of air shower array, burst
  detectors and emusion chambers were set up to
  closely observe the core region of an air shower
  event. The total area of them is 80 m2. Each
  burst detector is composed of a plate of plastic
  scintillator 160 cm (length) x 50 cm (width) x 2
  cm (thikness) and 4 photodiodes attached to each
  corner of the plate. On each burst detecter,
  placed were 6 layers of emulsion chambers (x-ray
  film interleaved with Pb plate). This hybrid
  experiment incorporating the air shower array,
  burst detectors emulsion chambers enables us to
  select and measure the proton component in
  primary cosmic rays in the "knee" region (10
  15-1016 eV).

63
Balloon-borne CR experiments with EC

• JACEE (1980-1996)
• 1Z26, E01012 - 51014 eV, W2-5 m2sr,
  ST107(H,He)/65(Zgt2) m2day
• MUBEE (1993-1995)
• 1Z26, E01013 - 31014 eV, W0.6 m2sr
• ST22 m2day
• RUNJOB (1995-1999)
• 1Z26, E01013 - 1015 eV, W1.6 m2sr
• ST575 m2hr

64
JACEE detector
65
RUNJOB detector