The basical cuts

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1. Comparing Z-Vertex in MVRT bank with GPID bank in sereral situations

All particles (proton, π+, and π-) use the same vertex in MVRT bank. However, they are different in GPID bank.
The folllowing table describes what particle's z-vertex we use in each topology.

γ p -> p π+ (π-)	GPID (proton z-Vertex)
γ p -> p π- (π+)	GPID (proton z-Vertex)
γ p -> π+ π- (p)	GPID (π+ z-Vertex)
γ p -> p π+ π-	GPID (proton z-Vertex)

(A) In the double-pion photo production

without CL cut

MVRT bank GPID bank
with CL cut (1%)

MVRT bank GPID bank

(B) In proton momentums of the several ranges

without CL cut

MVRT bank GPID bank
with CL cut (1%)

MVRT bank GPID bank

(C) In theta angles of the several ranges

without CL cut

MVRT bank GPID bank
with CL cut (1%)

MVRT bank GPID bank

2. The Cuts used by the FSU group now

To make the upper vetex plot, I have used the following fours kinds of cuts:

The vertex Cut
The beta Cut
The accidental Cut
The signal Cut

(A) The Vertex Cut

The vertex difference between particles (using GPID bank)
- | z-Vertex(proton) - z-Vertex(pi+) | < 5.0
- | z-Vertex(proton) - z-Vertex(pi-) | < 5.0
- | z-Vertex(pi+) - z-Vertex(pi-) | < 5.0
XY projection of the Vertex (using MVRT bank)
- | x-Vertex*x-Vertex + y-Vertex*y-Vertex | < 9

The vertex difference between particles (GPID bank)	XY projection of the Vertex (MVRT bank)

(B) The Bata Cut

The beta difference
- proton : -0.01882 < Δβ < 0.01882
- π+ : -0.0285 < Δβ < 0.0285
- π- : -0.0265 < Δβ < 0.0265

proton	π+	π-

(C) The Accidental Cut

The ngrf ( proton ngrf = π+ ngrf = π- ngrf = 1 )
The tagrid ( proton tagrid = π+ tagrid = π- tagrid )
proton mass_ref = π+ mass_ref = π- mass_ref = 0
The vertex_time = st_time - st_len/(beta*30)
- proton : 0 < vertex_time < 35.0
- π+ : 0 < vertex_time < 35.0
- π- : 0 < vertex_time < 35.0
- st_time : ST calibrated time fro this track [ns]
- st_len : track length from origin to ST [cm]
- 30 : the velocity of the light [cm/ns]

proton	π+	π-

(D) The Signal Cut

After applying the kinematic fitting, there are the 4 vectors of the proton, π+, and π- as the output. I try to make some missing mass plots using the 4 vertors.

In the case of topology γ p -> p π+ (π-),

MyInitial = (0.0, 0.0, E(photon), E(photon)+0.93827 )
MyPro_Sit01_KinF = the 4 vector of the proton in the topology γ p -> p π+ (π-) after applying the kinematic fitting
MyPip_Sit01_KinF = the 4 vector of the π+ in the topology γ p -> p π+ (π-) after applying the kinematic fitting

The following histogram is made using MissingMass.M2(). The peak around 0.02 should be one for the π-. I have applied some cut for this peak (Blue line)

The topology γ p -> p π+ (π-) : +0.012 < MyMissingVectorKinF.M2() < +0.026
The topology γ p -> p π- (π+) : +0.012 < MyMissingVectorKinF.M2() < +0.026
The topology γ p -> π- π+ (p) : +0.85 < MyMissingVectorKinF.M2() < +0.90
The topology γ p -> p π- π+ : -0.0081 < MyMissingVectorKinF.M2() < +0.0081

Sungkyun Park

Last modified: Now 01, 2010