[Comphep-common] COMPHEP for excited leptons - confirmation about the checks before production

Fri Oct 5 17:43:13 MSK 2012

Dear Experts,

I am writing again to this thread essentially regarding the two doubts I have:

(1) The process I am generating is pp->eeEE
with only Ex or ex as the propagator.
I get two feynman diagrams. Please find that attached (feynmanDiag.png).
In these two diagrams, I understand (by looking at the sign of arrow) that 
ex in both the cases is negatively charged. Am I missing the diagrams
with Ex as the propagator here?

(2) For this particular process if I require only Ex as the propagator, then 
I again get the two same diagrams as shown in feynmanDiag_withonlyEx_aspropagator.png
For this particular set, I expected only 1 diagram. 
Is something going wrong with the process? Or is this expected?

Thanks for your help,

Best Regards,
Shilpi

________________________________________
From: comphep-common-bounces at theory.sinp.msu.ru [comphep-common-bounces at theory.sinp.msu.ru] on behalf of Shilpi Jain [Shilpi.Jain at cern.ch]
Sent: 01 October 2012 22:11
To: dubinin at theory.sinp.msu.ru
Cc: comphep-common at theory.sinp.msu.ru
Subject: Re: [Comphep-common] COMPHEP for excited leptons - confirmation about the checks before production

Dear Edward, Mikhail,

Thanks a lot for explaining that to me and sending the links.
I went through the relevant part of the paper.
I have a few small doubts.
For all the cases, I understand that the arrow shows the particle flow
and not the momentum.
I could not get the exact
regularization scheme as given in the paper for
e+e- - > nubar + e- + u + dbar
On P-1041 of the paper, some of the members in the list
of regularization which I get ( and which do not match with the list given in the paper) are:
(P1+P2):  12 = M_gamma = 0 - diag 1
               12 = MZ  - diag  - diag 3

(P4-P1-P2): 412 = Melectron = 0 - diag 4
(P1-P3-P4): 134 = M_nu = 0 - diag 2

Moreover for my case, I get the following regularization for kinematic scheme ( u(1) + U(2) -> e(3) + e(4) + E(5) + E(6) ):

512, 612, 312, 412

[ Since 1 + 2 = 3 + e*. So for the propagator e*, its momentum is becomes  = 1 + 2 - 3 ]
Please let me know where I am going wrong.

Thanks & Regards,
Shilpi
________________________________________
From: Mikhail Dubinin [dubinin at theory.sinp.msu.ru]
Sent: 01 October 2012 10:14
To: Shilpi Jain
Cc: boos at theory.sinp.msu.ru; comphep-common at theory.sinp.msu.ru
Subject: Re: [Comphep-common] COMPHEP for excited leptons - confirmation about the checks before production

Dear Shilpi,

besides the manual, you can find two examples with many details
(particle numbering, regularizations, kinematical scheme, etc)

CMS twiki

https://twiki.cern.ch/twiki/bin/viewauth/CMS/Regularization

Survey in Uspekhi (example somewhere in the middle)

Edward Boos, Mikhail Dubinin, Problems of automatic calculation for
collider physics, Phys.Usp. 53 (2010) 1039-1051

Please look through these practical materials, hope a number of useful
recommendations can be found there.

Regards       Mikhail

On Sun, 2012-09-30 at 22:45 +0000, Shilpi Jain wrote:
> Dear Edward,
>
> Thanks for your response.
>
> (1) I put the width of resonance (0.0002173 GeV for 800 GeV mass e*)
> Since the process is:
>
> u(1) +U (2) -> e (3) + e* -> e (3) + e(4) + E(5) + E(6)
>
> whereas number in the bracket denotes the number of the particle
> in COMPHEP as I understand.
> I am still not sure about the particle numbering.
> In the manual, it is written that
> "It is assumed that particles are numerated in the same order as they are written down in
> the (sub)process name"
>
> Does this mean that if I put the process as u,U -> E, e, E, e while preparing
> my process (as shown in process.png)
> then the numbering will be like this:
> u(1), U(2) -> E(3), e(4), E(5), e(6)
>
> (2) I put the regularization as follows (also shown in attached regularization.png):
> ==========================================
> momentum | Mass | Width | power
> 312             | Mex  | wex    | 2
> ==========================================
>
> [ since P(e*) = P(e) - P(u) - P(U) ]
>
> But I get the error of "Bad precision" during vegas. This is shown in the attached vegas.png file.
>
> I think I am doing something wrong somewhere. Could you please help me
> in correcting this?
>
> Thanks a lot for your help,
> Best Regards,
> Shilpi
>
>
> ________________________________________
> From: Eduard Boos [boos at theory.sinp.msu.ru]
> Sent: 30 September 2012 17:42
> To: Shilpi Jain
> Cc: comphep-common at theory.sinp.msu.ru
> Subject: Re: [Comphep-common] COMPHEP for excited leptons - confirmation about the checks before production
>
> Dear Jian,
> If you have a resonance in the intermediate state you have to put the
> width of the resonance. Make sure, you did that and also introduce the
> corresponding "Regularization". You have 4-fermion interactions which
> violate unitary behaviour, so one should not be surprise with growing
> energy or pt distributions. Yes, the errors are in %.  If you put cuts,
> the cross section is the one from the corresponding kinematic area.
>
> Please, have a look into the CompHEP manual for details.
>
> Best, Edward
>
>
> > Dear Experts,
> >
> > I am running COMPHEP for the following process:
> > qqbar->e*e->e,E,E,e
> > i.e. e* decaying to 3 leptons via contact interaction.
> >
> > Just as a check I tried running for:
> > u+U->e,E,E,e
> >
> > (1) I got two feynman diagrams.
> > Please find attached feynmanDiag.png
> > I understand that these two diagrams correspond to
> > e*+ in one and e*- in the other.
> > Do you think this is correct?
> >
> >
> > (2) The kinematic scheme showed by COMPHEP (also attached:
> > kinematic_scheme.png) is as follows:
> > u,U->e,e,E,E
> > =========================================================
> > in=12   -> out1=3  out2 =456
> > in=456 -> out1=4  out2=56
> > in=56  ->  out1=5  out2=6
> > =========================================================
> > I am not sure about how the naming of the particles is done.
> > I understand that 456 always refer to the particles coming out from e* and
> > 3 refers to the
> > one which is produced in conjunction with e*.
> > This scheme is valid for both the feynam diagrams
> > Do you think this understanding is correct?
> >
> >
> > (3) After putting Itmax=10 ; ncalls = 9720,
> > Please find the result of numerical calculation attached (please find
> > comphepNumericalSession.ng attached).
> > The final xsec is: 3.035e-3 with an error of 4.59e-1. Is this error in %?
> > So the final error is
> > 4.59e-1 times 3.035e-3?
> >
> > Do you think the results are fine?
> >
> > (4) I get the following distributions for E4, M456 (please find pt4.png
> > and M456.png attached)
> > I see that:
> > (a) cross-section is increasing with E4. Shouldn't it start decreasing
> > after some point?
> > (b) M456 should have peaked at 400 since I understand that 456 are coming
> > from the decay of e*.
> > It is peaking but it is not sharply peaked.
> >
> > All these distributions are done for pT of the outgoing particles > 15 GeV
> > and |eta| < 3.1
> >
> > Do you think something is wrong going here?
> >
> > Please let me know if you require more input from my side.
> >
> > Thanks for your help,
> > Best Regards,
> > Shilpi Jain
> >
> > _______________________________________________
> > Comphep-common mailing list
> > Comphep-common at theory.sinp.msu.ru
> > http://theory.sinp.msu.ru/mailman/listinfo/comphep-common
> >
>
> _______________________________________________
> Comphep-common mailing list
> Comphep-common at theory.sinp.msu.ru
> http://theory.sinp.msu.ru/mailman/listinfo/comphep-common

_______________________________________________
Comphep-common mailing list
Comphep-common at theory.sinp.msu.ru
http://theory.sinp.msu.ru/mailman/listinfo/comphep-common
-------------- next part --------------
A non-text attachment was scrubbed...
Name: feynmanDiag.png
Type: image/png
Size: 42776 bytes
Desc: feynmanDiag.png
URL: <http://theory.sinp.msu.ru/pipermail/comphep-common/attachments/20121005/ee46e7a4/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: feynmanDIag_withonlyEx_aspropagator.png
Type: image/png
Size: 45838 bytes
Desc: feynmanDIag_withonlyEx_aspropagator.png
URL: <http://theory.sinp.msu.ru/pipermail/comphep-common/attachments/20121005/ee46e7a4/attachment-0005.png>