1. The first row is for one of the daughters has a ssd hit
2. The second row is for both dauhgters have a ssd hit

K0-Short when the dca between the 2 daughters decreases from 0.8 to 0.5

1. The first row is for one of the daughters has a ssd hit
2. The second row is for both dauhgters have a ssd hit

• It seems that included one daughter or the 2 daughters with a ssd hit decrease the background but decrease the signal too. There is apparently no improvement on the mass (or very small) and on the sigma on it.
• For comparison, the next plots are the same but for the daughters which haven't a ssd hit. The initial background is bigger but when I apply the same cut I got roughly the same : - here
  

Lambda when the decay length increases from 2 cm from 8 cm

1. The first row is for one of the daughters has a ssd hit
2. The second row is for both dauhgters have a ssd hit

Lambda when the dca between the 2 daughters decreases from 0.8 to 0.5

1. The first row is for one of the daughters has a ssd hit
2. The second row is for both dauhgters have a ssd hit

Fit of the invariant mass

• DecayLengthV0 > 2
• daughters < 0.8
• dcaParentoPrimVtx < 0.5
• tpchits_neg>15 && tpchits_pos>15

Figure 1 : K0 candidates without the ssd	Figure 2 : K0 candidates which one daughter has a point in the ssd

Update of this page May 24th

For the K0-SHORT

Figure 1 : No ssd : up : decay , down : dca of the daughters	Figure 2 : Decay length	Figure 3 : Dca between the 2 daughters

For the Lambda

• For figures 2 and 3, the upper plots refers to the daughters which have only 1 ssd hit (the positive or the negative pos.), while the plots on the bottom were for both the daughters have a ssd hit.
• The decay length is increasing from 2cm, 4cm, 6cm and 8 cm
• The dca between the daughters is deceasing from 0.8cm, 0.7cm, 0.6cm and 0.5 cm.

Figure 1 : No ssd : up : decay , down : dca of the daughters	Figure 2 : Decay length	Figure 3 : Dca between the 2 daughters

Invariant mass as a function ot pT

• pT < 1 GeV/c
• 1 < pT < 2 GeV/c
• pT >2 GeV/c

• Again the first row refers to the K0 which only one daughter has a ssd point whereas the second row is for the 2 daughters which have ssd points.

KO-SHORT

Figure 1 : pT < 1	Figure 2 : 1 < pT < 2	Figure 3 : pT > 2

Lambda

Figure 1 : pT < 1	Figure 2 : 1 < pT < 2	Figure 3 : pT > 2

• The highest number of V0 found is for pt < 1
• When we look for the daughters which have 2 ssd points, the number of V0 found decreases because of the statistic (peak) and the background too. This effect is more seeing for the Lambda with 1 < pT < 2 ; when we first look at the V0 where one of the daughters has a ssd point, the background is already well suppressed.
  But when I also looked at the V0 which don't have ssd points (see the next figure 4), the background is also already suppressed for this range of pT, so this is not a effect only for the tracks included a ssd point.

  Figure 4 : 1 < pT < 2, no ssd point for the daughters