This is a description of a package called MFINDR adapted
to fit photon pairs to Pi0, Eta and Eta primes using E852
data.
The library required to link is "mfindr.o" in the
/home/lemond/e852/lib.irix5 directory, with the corresponding
RS6000 version, named "mfindr_i.o", in
/home/lemond/e852/lib.rs6000.
In the absence of covariant matrices for photons the following
input errors are suggested (see below):
sigma(E) = ( ( 2 + ( 6 / sqrt(E) ) ) / 100 ) * E, The energy;
sigma(theta) = 0.028 * theta, The polar angle;
sigma(phi) = 0.028 * phi, The azimuthal angle .
The current version is preliminary with future improvements
and additions possible.
Usage
-----
In order to utilise this package, the following two (FORTRAN)
routines need to be called.
(N.B.
For the purposes of this description,
(a) it is assumed that this package is called from
within a "C" program,
(b) the word meson(s) generically refers to Pi0, Eta,
Eta prime, or a combination thereof as determined
by the value of the integer "imcode" below. )
1-
ebpini(imcode, idump)
where,
imcode is an integer with the following possible values:
imcode = 1 ----> only Pi0 fits are attempted,
imcode = 11 ----> only Pi0 and Eta fits are attempted,
imcode = 111 ----> Pi0, Eta and Eta prime fits are attempted.
idump is an integer with the following possible values:
idump = 1 ----> Provides limited dumping of information
in a separate file (unit 25) from the
standard output file. This would be
appropriate for debugging and/or dumping
of a small number of events,
idump = 0 ----> No dumping carried out.
This routine should be called only once in the initialization
stage of the ("main") analysis program.
2-
ebpift( NGAMMA, GP4, GERR, npar, npardx, mesatt, mesmas, meschi,
mesflg, mesbst, pull )
where
INPUT
-----
NGAMMA = (integer) Total number of photons to be used,
GP4(L1, M1) = (real) The 4-momentum (L1=1,4 -> Px, Py, Pz, E)
for each photon number M1,
Maximum size of L1 is 20
Maximum size of M1 is 30
GERR(L1, M1) = (real) The photon errors for each photon number M1;
L1=1 --> sigma(E)/E See above,
L1=2 --> sigma(theta)/theta " "
L1=3 --> sigma(phi)/phi " "
Maximum size of L1 is 20
Maximum size of M1 is 30
OUTPUT
------
npar(k) = (integer) k = 1 --> Number of photons (for self-
containment and consistency),
k = 2 --> Total Number of fits (or mesons),
k = 3 --> Number of gamma-gamma combinations
k = 4 --> Number of Pi0s,
k = 5 --> Number of Etas.
k = 6 --> Number of Eta primes.
Maximum size of k is 20
npardx(L2, M2) = (integer) L2 = 1 --> fit index
L2 = 2 --> fit's identification
number (7 for Pi0,
17 for Eta, 30 for Etaprime)
L2 = 3 --> photon-pair index
(= gamma1 index * 1000 +
gamma2 index)
L2 = 4 --> photon-pair mass flag
flag = 1. for pi0,
flag = 2. for eta,
flag = 3. for eta prime,
M2 --> fit(meson) number
Maximum size of L2 is 20
Maximum size of M2 is 10
mesatt(L3, M3) = (real) L3 = 1- 5 --> meson's Px, Py, Pz, E, P
respectively
L3 = 6-10 --> absolute errors for the above
L3 = 11 --> reconstructed meson mass
M3 --> meson number
Maximum size of L3 is 40
Maximum size of M3 is 10
mesmas(L4, L5) = (real) pair mass of photons L4 and L5
Maximum size of L4 is 20
Maximum size of L5 is 20
meschi(L6, L7) = (real) pair chi**2 of photons L6 and L7
Maximum size of L6 is 20
Maximum size of L7 is 20
mesflg(L8, L9) = (real) meson mass flag of photons L8 and L9
flag = 1. for pi0,
flag = 2. for eta,
flag = 3. for eta prime,
Maximum size of L8 is 20
Maximum size of L9 is 20
mesbst(L10, M4) = (real) L10 = 1 --> Best pair mass
L10 = 2 --> Best pair chi**2
L10 = 3 --> Best pair Confidence Level
M4 = pair number
Maximum size of L10 is 20
Maximum size of M4 is 10 .
pull(L11, M5) = (real) L11 = 1 --> Pull in the polar
angle (theta) of
photon # 1 in the
pair combination M5
L11 = 2 --> Pull in the azimuthal
angle (phi) of photon # 1
L11 = 3 --> Pull in the polar
angle (theta) of photon # 2
L11 = 4 --> Pull in the azimuthal
angle (phi) of photon # 2
L11 = 5 --> Pull in Mass of photons
1 & 2 in combination M5
M5 = Pair combination of photons 1 & 2.
Maximum size of L11 is 20 .
Maximum size of M5 is 400 .
Note:
----
This routine should be called only once per event in the
analysis program.
This package maybe utilised in a generalized form whereby only
the information coming from all the gamma-gamma combinations
is used (mesmas & meschi), hence, permitting the user to make
selections based upon that information.
Alternatively, or additionally, the user may take advantage of
the fit results (mesatt, mesbst & pull) of the meson pair
reconstruction.
------------------------------------------------------------
The following points should be noted:
a)
The maximum number of input photons allowed is 20, otherwise
only the first 20 photons are considered by the fitter.
b)
The input photon attributes (GP4) should be provided consecutively
for photons with index 1 to NGAMMA).
c)
Future improvements will include handling of merged-photons
(single-cluster mesons) capability, if required.
d)
This package does not carry out any vertex fitting.
Please refer all relevant queries and bug reports to me.
Amir H Sanjari