Today's Progress 19. Dec. 2007

Deuteron spectra (2)

Since deuteron PID on PA-PB-NT has been improved and the events from in-flight reaction on PA could be eliminated now with energy-VS-1/&beta correlation by PA, deuteron spectra are reconsidered.

PA-originated events and deuteron spectrum

Since T0-PA 1/&beta and dE/dx are now availeble, we studied the correlations between them for "deuteron" events identified by 1/&beta by PA-PB and PB-NT total energy.

A correation between 1/&beta by T0-PA and dE/dx on PA for "deuteron" events. very fast component with small dE/dx is clearly seen.

As shown, &pi component is seen. This implies the d was &pi at the entrance of PA, then converted into d by &pi ¹²C -> d X reaction.

A correation between 1/&beta by PA-PB and dE/dx on PA for "deuteron" events. 3 components are clearly seen.

We have clearly observed 3 components on the correlation between 1/&beta by PA-PB and dE/dx on PA. To reveal the nature of the component with the second-smallest dE/dx, we compare two correlations below.

The comparison of the correlations previously shown. The component with the second-smallest dE/dx on right-hand correlation having middle-range 1/&beta on T0-PA, which corresponds to proton.

The component with the second-smallest dE/dx on PA is considered to be the proton-induced deuteron by p ¹²C -> d X reaction. Therefore, "deuteron" events identified by 1/&beta by PA-PB VS total energy on PB+NT are found to be contaminated by reaction product on PA, and further event selection is required by using PA-related quantities. We introduce event selection with 2D correlation between 1/&beta by PA-PB and dE/dx on PA for "deuteron" events at PB+NT as drawn nextly.

The defined event selection is shown below. We divide the 2D-region of 1/&beta by PA-PB and dE/dx on PA into four subcomponents, namely, signal, I, II, III.

Definition of events selection

Correlations between 1/&beta by T0-PA and dE/dx on PA are shown below for the defined 2D regions.

signal

component I

component II

component III

According to them, all of I/II/III components are found to be reaction product on PA, hence they must be eliminated from inclusive ⁴He(stopped K^-,d) spectrum and further Yd analysis. The event summary is given below.

Deuteron event statistics 1
Deuteron statistics in E549/E570(1st+2nd cycles)/E549+E570.
2D region identified "deuteron" number (A) "deuteron" number after succsefull energy loss correction (B) Survaival ratio (B/A)

"deutaron" all 46613/65846/112459 41525/59612/101137 0.891/0.905/0.899

signal (⁴He(stopped K^-,d)X) 37446/52108/89554 34905/49455/84360 0.932/0.949/0.942

region I(II or III at the middle of PA) 1123/1748/2871 871/1411/2282 0.776/0.807/0.795

region II(¹²C(in-flight p,d)X on PA) 3664/5349/9013 3056/4494/7550 0.834/0.840/0.838

region III(¹²C(in-flight &pi^+-,d)X on PA) 4380/6641/11021 2693/4252/6945 0.615/0.640/0.630

Deuteron event statistics 1
Deuteron statistics in E549/E570(1st+2nd cycles)/E549+E570.
2D region	identified "deuteron" number (A)	"deuteron" number after succsefull energy loss correction (B)	Survaival ratio (B/A)
"deutaron" all	46613/65846/112459	41525/59612/101137	0.891/0.905/0.899
signal (⁴He(stopped K^-,d)X)	37446/52108/89554	34905/49455/84360	0.932/0.949/0.942
region I(II or III at the middle of PA)	1123/1748/2871	871/1411/2282	0.776/0.807/0.795
region II(¹²C(in-flight p,d)X on PA)	3664/5349/9013	3056/4494/7550	0.834/0.840/0.838
region III(¹²C(in-flight &pi^+-,d)X on PA)	4380/6641/11021	2693/4252/6945	0.615/0.640/0.630

Deuteron momentun spectra for all(black)/signal(red)/I(green)/II(yellow)/III(magenta) components. About 50% of un-physical high energy BG is found to be produced by III component.

About a half of unphysical BG orginates from III component. Since dE/dx on PA is not sensitive for the in-flight reaction in front of PA, tiny unphysical high-energy BG is unavoidable, in principle.

Test with dn/dp back-to-back events

Though I/II/III components are considered to be unphysical, we should confirm it. The confirmation is actually performed by back-to-back dp/dn events. When the d is really unphysical, we do not expect any hyperon on the mass spectrum. Here, we examine it. As used to be so, black/red/green/yellow/magenta are used for all/signal/I/II/III, respectively.

dp result

dn result

Summary

Deuteron event statistics 2
Deuteron statistics in E549+E570.
2D region	identified "dp" event number	identified "dn" event number	dp/inclusive dn/inclusive number ratios
"deutaron" all	5626	9506	0.0500/0.0845
signal (⁴He(stopped K^-,d)X)	5189	8186	0.0579/0.0914
region I(II or III at the middle of PA)	79	202	0.0275/0.0704
region II(¹²C(in-flight p,d)X on PA)	154	488	0.0171/0.0541
region III(¹²C(in-flight &pi^+-,d)X on PA)	204	630	0.0185/0.0572

In conclusion, we could identify clear &Lambda/&Sigma^- signals only in "signal" component. We consider the event selection introduced here works properly, and adopt it to define "deuteron", hereafter.

Acceptance corrected inclusive spectrum after BG subtraction

Because the deuteron acceptance correction and normalization used to be discussed here, we just operate the corection to the updated inclusive spectrum. Physical structures are expected be more emphasized, as the result.