[Blackmax] Questions on string ball cross sections in BlackMax

[Kwok, Martin]

Sorry for the spam -- message was rejected by the blackmax project server
for oversized email. I have replaced the attachments with links.

---------------------------------------------------------
Dear BlackMax authors and Prof. Gingrich,

As a member of the CMS blackhole analysis team, I would like to seek your
advice on some interesting observation while using BlackMax to calculate
string ball cross sections.
We observe that, the string ball cross section remained roughly constant
despite the fall of parton distribution function as minimum black hole mass
increases.
More specifically, we studied parameter set 1 [1] in details and obtained
the following cross sections:
minimum BH/SB mass = 6 TeV  cross section = 7.41 E-02 pb
minimum BH/SB mass = 7 TeV  cross section = 6.90 E-02 pb
Whereas for parameter set 2 [3], the cross section drops by an order of
magnitude for the same increase in minMBH.

For both parameter set 1 and 2, the parton-level cross section should
remain constant as M_s/gs < M_SB < M_s/gs^2. To see this works in BlackMax,
I plotted [3] the parton-level cross section factor pi*(r_max-r_min) as the
code samples different M_BH during the calculation for cross section.
Interestingly, if we use minMBH=6TeV in parameter set 1 as input (Red
dots), the factor decreases up to 2 orders of magnitude for same M_BH below
the SB-BH transition(8TeV) and for minMBH=7TeV(Blue dots), there is no such
decrease. I think this effect compensated the drop of PDF and kept the
cross section constant when we go from 6 TeV to 7 TeV.

Could you explain what is the physical reason for the variation of
parton-level cross section for given M_BH? And more interestingly, why
would the behaviour be different for minMBH =6 and 7TeV? For your
reference, I also attach the same plot [4] calculated with a different
parameter set [3].

For your ease of reproducing the problem, I have attached the input
parameter files to produce the plot [5],[6] and I am using BlackMax-2.02.
Please let me know if you need any further information on the conditions
for producing these results.
Thanks a lot for your help.

Best,
Martin


[1] Parameter set 1 (SB_EXTRA4): M_D=2.38 TeV, M_s=  2  TeV, gs=0.5
(M_s/gs^2 =  8     TeV)
[2] BM_SB_EXTRA4_xsec_parton.pdf
https://drive.google.com/open?id=0B-LlizIXYvNVcVBtZlJCMXI1R3RaU2JtZlZBNHpscmVGZ3A0

[3] Parameter set 2 (SB_EXTRA2): M_D=1.49 TeV, M_s=1.1 TeV, gs=0.3
(M_s/gs^2 ~12.2 TeV)
[4] BM_SB_EXTRA2_xsec_parton.pdf
https://drive.google.com/open?id=0B-LlizIXYvNVLUpCdnVFRVNpVzFRYVMzMWxQT2xad1lvS05V

[5] SB_EXTRA4_MBH6000_n6_custom.txt
https://drive.google.com/file/d/0B-LlizIXYvNVT2p2bU5SamdEbHhobjdYRG93U052UXNUWXNR/view?usp=sharing
[6] SB_EXTRA4_MBH7000_n6_custom.txt
https://drive.google.com/file/d/0B-LlizIXYvNVLXVNSlZpd0pxOG92ejJUYmJVN3E3NmlORGNB/view?usp=sharing

On Mon, Sep 12, 2016 at 2:49 AM, Kwok, Martin <ka_hei_martin_kwok at brown.edu>
wrote:

> Dear BlackMax authors and Prof. Gingrich,
>
> As a member of the CMS blackhole analysis team, I would like to seek your
> advice on some interesting observation while using BlackMax to calculate
> string ball cross sections.
> We observe that, the string ball cross section remained roughly constant
> despite the fall of parton distribution function as minimum black hole mass
> increases.
> More specifically, we studied parameter set 1 [1] in details and obtained
> the following cross sections:
> minimum BH/SB mass = 6 TeV  cross section = 7.41 E-02 pb
> minimum BH/SB mass = 7 TeV  cross section = 6.90 E-02 pb
> Whereas for parameter set 2 [3], the cross section drops by an order of
> magnitude for the same increase in minMBH.
>
> For both parameter set 1 and 2, the parton-level cross section should
> remain constant as M_s/gs < M_SB < M_s/gs^2. To see this works in BlackMax,
> I plotted [3] the parton-level cross section factor pi*(r_max-r_min) as the
> code samples different M_BH during the calculation for cross section.
> Interestingly, if we use minMBH=6TeV in parameter set 1 as input (Red
> dots), the factor decreases up to 2 orders of magnitude for same M_BH below
> the SB-BH transition(8TeV) and for minMBH=7TeV(Blue dots), there is no such
> decrease. I think this effect compensated the drop of PDF and kept the
> cross section constant when we go from 6 TeV to 7 TeV.
>
> Could you explain what is the physical reason for the variation of
> parton-level cross section for given M_BH? And more interestingly, why
> would the behaviour be different for minMBH =6 and 7TeV? For your
> reference, I also attach the same plot [4] calculated with a different
> parameter set [3].
>
> For your ease of reproducing the problem, I have attached the input
> parameter files to produce the plot [5],[6] and I am using BlackMax-2.02.
> Please let me know if you need any further information on the conditions
> for producing these results.
> Thanks a lot for your help.
>
> Best,
> Martin
>
>
> [1] Parameter set 1 (SB_EXTRA4): M_D=2.38 TeV, M_s=  2  TeV, gs=0.5
> (M_s/gs^2 =  8     TeV)
> [2] BM_SB_EXTRA4_xsec_parton.pdf
>
> [3] Parameter set 2 (SB_EXTRA2): M_D=1.49 TeV, M_s=1.1 TeV, gs=0.3
> (M_s/gs^2 ~12.2 TeV)
> [4] BM_SB_EXTRA2_xsec_parton.pdf
>
> [5] SB_EXTRA4_MBH6000_n6_custom.txt
> [6] SB_EXTRA4_MBH7000_n6_custom.txt
>
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