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d+Au ridge: Fluctuation in TPC-FTPC Au side Dihadron Correlation

Updated on Tue, 2014-05-06 21:25. Originally created by yili on 2014-05-04 20:50.

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The TPC-FTPC Au Dihadron Δφ correlation has large fluctuation.

Here is real/mix signal histogram:

Fig 1.

Look the red point for the ZDC central 0-20%. There are several jumps for those red point. For example, around Δφ=2.7.

So we look into real and mix events separately.

Real event:

Fig 2.

Mix event:

Fig 3.

From the mix events, the boundary effect is clearly shown. The real event seems also show this feature, but not clear.

When do real/mix:

Fig 4.
 

The points jump up and down. Since the boundary effect is not clear in real event, but is clear in mix event. The ratio real/mix gains more structure than real event along.

However, this itself cannot explain all the large fluctuations.

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1. -------------------------------------TPC x FTPC --------------------------------------------------

For the mix event, we do FullField (B>0) and ReserveFullField (B<0) separately for different charge combinations.

Let's look at the case both the trigger and associate particles are negative charges.

1. FullField: Real event vs Mix event: (ignore the title. it is 1-3 GeV/c)

Fig 5.

It is hard to tell whether they are matched or not.

2. ReserveFullField: Real event vs Mix event (ignore the title. it is 1-3 GeV/c)

Fig. 6

It seems matched (those dips).

3. Mix event: RF vs FF

Fig. 7

They are shifted by 1 or 2 bins.

4. Real Event: RF vs FF

Fig. 8
 

Hard to say.

5. Merge RF and FF together: Real vs Mix (ignore the title. it is 1-3 GeV/c)

Fig. 9

Not clear to me.

2. -------------------------------------TPC x TPC --------------------------------------------------

However, the same method/code looks fine for TPC x TPC correlations

1. real event:

Fig. 10

Clear patterns.

2. Mix event:

Fig. 11

Patterns.

3. real/mix: (1D divided by 1D)

Fig. 12

Pattern corrected by mix event.

--> Why the same code work for TPC x TPC but make TPC x FTPC worse??

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Single Particle φ distribution

1. TPC:

Fig. 13

12 dips. one dip at -0.23

2. FTPC:

Fig. 14

6 dips. one dip at -0.65

So for TPC x FTPC correlation, one dip will be at -0.33. While, it is not the dip we see from the mix event.

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