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how to convert kinematic variables from lab frame to cm frame in root [message #14826]

Mon, 03 June 2013 08:56

Ajay Kumar
Messages: 102
Registered: December 2011
Location: indore

continuous participant

From: *iitidr.ac.in

Hello everyone,

I know the Theta distribution of two body decay reaction in the laboratory frame.I need to convert Theta_lab distribution in to Theta_CM distribution for my analysis.
For this , I have searched in the ROOT user guide but unfortunately I could not see any functionality there for that.

How to convert different kinematic variables from lab frame to cm frame using root?

Is there any functionality available in root for this conversion?

Thanks

AJAY KUMAR
Research scholar
Indian Institute of Technology Indore,Indore
Madhya Pradesh
India

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Re: how to convert kinematic variables from lab frame to cm frame in root [message #14827 is a reply to message #14826]

Mon, 03 June 2013 09:32

Ralf Kliemt
Messages: 507
Registered: May 2007
Location: GSI, Darmstadt

first-grade participant

From: *gsi.de

Hello,

There are two situations:

A) If you do analysis, there is the
RhoBooster class which helps transforming the particle candidates between LAB and CM.

B) You use TLorentzVector: There is the possibility to boost it with the CM momentum.
(see also http://root.cern.ch/root/html534/TLorentzVector.html)

Cheers.
Ralf

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Re: how to convert kinematic variables from lab frame to cm frame in root [message #14831 is a reply to message #14826]

Mon, 03 June 2013 15:19

Stefan Pflueger
Messages: 99
Registered: February 2012

continuous participant

From: *kph.uni-mainz.de

Hi Ajay,

just a small remark: I also had to calculate this for lmd fitting. However my function calculates the 4 momentum transfer from the theta angle in the lab frame. You can see it here

http://cbmroot.gsi.de//panda_doc/daily/html/classPndLmdDPMAngModel1D.htm l#ab105732897c38a7fa0aaf679dcb2bd11

Maybe this is of some use..

Best regards,

Stefan

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Re: how to convert kinematic variables from lab frame to cm frame in root [message #14832 is a reply to message #14827]

Mon, 03 June 2013 19:31

StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino

first-grade participant

From: 2.235.190*

This means that, if you have a collision along z axis, you can calculate the beta of the center of mass (betacm), and transform one TLV from lab to cm you have just to do:

tlv_lab.Boost(0., 0., betacm);

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Re: how to convert kinematic variables from lab frame to cm frame in root [message #14895 is a reply to message #14831]

Tue, 25 June 2013 09:18

Ajay Kumar
Messages: 102
Registered: December 2011
Location: indore

continuous participant

From: *iitidr.ac.in

Dear All,

Thanks to all of you.
I have boosted Lambda and AntiLambda from lab to cm frame using TLorentzVector.
I have attached macro here.Please see it once,

Am I doing correct ?
Please help me.

Thanks

Attachment: run_labcm_conversion.C
(Size: 2.85KB, Downloaded 377 times)

AJAY KUMAR
Research scholar
Indian Institute of Technology Indore,Indore
Madhya Pradesh
India

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Re: how to convert kinematic variables from lab frame to cm frame in root [message #14896 is a reply to message #14895]

Tue, 25 June 2013 10:20

StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino

first-grade participant

From: *to.infn.it

No, it is not correct.
First of all, you have to calculate the betacm from the initial particles (the target proton at rest and the projectile antiproton), and not from the supposed reconstructed lambdas.
Second, if your CM is traveling at betacm, in order to have the coordinates in the CM frame you have to boost them of -betacm.

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