Paper: Search for Lepton Flavor Violation in the emu Continuum

Comments due in CDS by: 20th Feb.

1.69: Motivate or reference "0.72" and "0.28"

2.13 and 2.14: It is just stylistic, but for consistency with places above where eta is mentioned, use the smaller sign instead of the equal sign.

2.37: It is just stylistic, but if you say 0.5 GeV instead of 500 MeV then all energy/momentum units in the paper will be GeV and makes things consistent. Also, the brain compares easier 0.5 GeV with 25 GeV than it would compare 500 MeV with 25 GeV.

2.51: It is just stylistic, but you can replace "transverse energy" with its symbol "E_T", to be consistent with the phrase above about the "p_T". It also saves space.

2.58: You say "missing transverse momentum" and denote it "ETmiss". Then it should be "missing transverse energy".

No, it's a vector quantity and in ATLAS we properly call it missing transverse momentum, if they call it missing transverse energy they'll be asked to change it back. (James F)

2.65: How does the single top process produce two prompt leptons, one being an electron and one being a muon and both leptons having opposite electric charge?

3.50: "two hypothesis" -> "two hypotheses"

3.54: "convoluting" might be in fact "convolving"?

3.59: "Fig 1." -> "Fig 1. a)"

3.66: "Fig 1." -> "Fig 1. b)"

4.16: "and in" -> "and"

Ref 15: For JHEP papers, the journal name must have 4 digits, where typically the first two are the digits of the year. For this paper might be 1012. A paper is found there on Spires, but must be double checked this is the paper indeed intended to reference.

Ref 18: Same as above. "07" -> "0207"

Ref 24: Same as above, but I could not guess what the year is from "001", also because the page is atypically only with two digits. Needs double check.

The paper is generally pretty good and presents an interesting search for RPV SUSY.

A) The paper neglects to mention of searches at HERA which are sensitive to the same physics:

stop production via R-parity violating SUSY:

This is a 90 degree rotation of the diagram for 1. The HERA experiments set limits on $\lamba_{131}$. See

H1 Collab., F.D. Aaron et al., Eur.Phys.J.C71 (2011) 1572

ZEUS Collaboration; S. Chekanov et al. Eur. Phys. J. C 50 (2007) 269

it would be nice to at least reference them.

B) Couldn't this process also occur via t-channel exchange of a LFV leptoquark?

like those in:

H1 Collab., F.D. Aaron et al., Phys. Lett. B701 (2011) 20 ,

would the present search also be able to improve on those exclusions?

C) What about signal processes like $d \bar{d} \rightarrow \tau \bar{\mu}$ with leptonic tau decay, were they considered?

D) What about processes such as $u \bar{b}\rightarrow e \mu$ are they perhaps constrained by B-physics measurements, if not why ignore them? (apart from the relatively small PDFs)

page 1 line 42-43: "The diagram ...has the same cross section" probably better as "The process ... has the same cross section"

page 1 line 65-66: sloppy phrasing here, the strange PDFs don't suppress the $ss \rightarrow e\mu$ process, without them it wouldn't happen at all, please reword.

page 1 line 69: More needs to be said about the 0.72 and 0.28, e.g. which PDF set is used to get this weighted sum, what is the associated uncertainty? How stable vs choice of alternative PDF? We need to know this to judge whether the limit vs coupling plot makes any sense.

references:

I agree with Adrian on the JHEP references, I don't know however if the paper is following some established ATLAS convention.

o p1 line 6:
I thought LPV is a general feature of GUT models, an even more convincing
extension. Not sure how to get a ref.
o p1 line 33:
Why is the top squark taken to be the lightest up type squark? Is it because
limits are set lowest? I assume b squark is more massvive. So I agree with James on this.
o line 35, page 3: Standard ATLAS tools needs a ref or description.
o Fig 2: dont understand the "total background". Signal hard to see
at all on dphi and nJet plot. The preselection tells one that
the top is understood but the final selection has no top visible. The issue
is to ensure tha tthe kinmatic distribution of diboson is correct.
Also, the instrumental suffers low statistics and the tails could
be an issue. It does not seem these plots are of any use in the final analysis.
o Fig 3: seems that in the end this is just a counting experiment
and it is hard to see where the kinematic cuts help.

Agree with others that a reference is needed for 0.72 and 0.28 pdfs, and that "using standard ATLAS tools" instead needs a description or a reference. Few minor comments:

p1, line 46 pluralised \lambda's could be confusing - would \lambda' indices be better?

p1, line 63 This sentence could be moved to line 51 - in its current position it reads as though the number of variables the cross section is dependent on has been simplified by ignoring s\dbar and d\sbar, but these are also only dependent on \lambda'_231 and \lambda'_132. Or change the sentence to have |\lambda'_131\lambda'_231| , |\lambda'_132\lambda'_232| and m_t~ as the three variables.

p2, line 30 "and with et>25Gev and to lie inside..." sentence too long, I think "and to lie" doesn't make sense. Perhaps "...reconstructed in the ID. They are required to have Et>25GeV and to lie inside..."

p3, line 34: "and were calculated" -> "were calculated"

4, line 33,: should reference 13 be a footnote instead?

-- DeepakKar - 2012-02-14