Forum: DM - Indirect Detection – Topic: Discussion Session 5/3/12

Tracy Slatyer (Institute for Advanced Study) will be leading the discussion on Christoph Weniger’s claim of a line in the FERMI data. Weniger’s analysis can be accessed here.

Forum: LHC - jets – Topic: Discussion Session 4/12/12

David Krohn (Harvard) will lead the discussion session on the ATLAS analysis for jet mass and substructure, available here.

Forum: Flavor Physics – Topic: Discussion Session 3/22/12

The slides for the forum are here.

Forum: Flavor Physics – Topic: Discussion Session 3/22/12

Joachim Kopp (Fermilab) will lead the discussion on the recent Daya Bay results for the measurement of theta-13. The link to the analysis can be found here.

Forum: LHC - leptons + X – Topic: Discussion Session 3/1/12

The CMS analysis with 1.1 fb^-1 can be found here. Some preliminary results for the update to 4.7 fb^-1 can be found here.

Forum: LHC - leptons + X – Topic: Discussion Session 3/1/12

Brian Batell (University of Chicago) will lead the discussion on t’ searches in the dilepton channel.

Forum: LHC - leptons + X – Topic: Discussion Session 2/2/2012

Jose Santiago (CAFPE & Universidad de Granada) will be leading the discussion on the ATLAS search for heavy vector-like quarks.

The ATLAS note can be found here.

Forum: LHC - photons + X – Topic: Discussion Session 1/10/12

Jessie Shelton (Yale U.) will be leading the discussion on the results of the recent Higgs searches. The links to the relevant papers are below.

CMS diphoton

CMS 4 leptons

CMS combined

ATLAS diphoton

ATLAS 4 leptons

ATLAS combined

Forum: General – Topic: Upcoming Talk Schedule

With the combined ATLAS/CMS Higgs search updates set to be announced on 12/13, we would like to have a forum on that on 12/15. Volunteers welcome.

Forum: General – Topic: Upcoming Talk Schedule

12/8/11: Alexey Petrov (Wayne State University) will lead the discussion on CP violation in D-meson decays. Forum link

Forum: Flavor Physics – Topic: Discussion session 12/8/11

Alexey Petrov (Wayne State University) will lead the discussion session on the recent analysis of CP violation in D-meson decays. Link to the slides from LHCb can be found here

Forum: LHC - photons + X – Topic: Discussion Session 11/17/11

The link to the CMS note is here

Forum: LHC - leptons + X – Topic: Discussion Session 10/13/11

We’ve recent started the LHC Results Forum where theorists present individual analyses from the LHC so as to better understand the details of high profile analyses. The first meeting covered the ATLAS bjet + lepton + MET analysis.

The forum was impressed with the analysis and we had a few small comments.

1. We had a bit of trouble following the discussion on the normalization of the background. In Sec. 2, the analysis says that QCD is data driven, and later say you use fix-order theoretical inclusive cross sections for top and W&Z+jets. Then in Section 4 the analysis normalizes the number of expected events in the signal region by $N_{sig data} = N_{sig MC} \times (N_{CR data}/ N_{CR MC})$.
   Is the purpose of using NⁿLO cross sections is to get the relative contribution of the different backgrounds? When the plots are made with the different background contributions labeled, is this rescaling already performed? I’ve talked to Pelle Hansson and think I understand the answers to these questions, but on the first pass it was difficult to follow. A sentence in Sec. 2 sign-posting how the backgrounds will be normalized in the signal region might clear it up.

   The MC prediction for top and W&Z+jets processes is normalized using NNLO cross sections. This normalization is used to show the background contributions in all the plots and to get the MC based estimate of the number of background events in the signal region and in the control region, respectively $N_{sig MC}$ and $N_{CR MC}$. However, we don’t use directly this estimate from MC ($N_{sig MC}$) to derive the exclusion limits but we use a semi-data driven approach where the MC estimate is rescaled using the number of observed events in the control region ($N_{CR data}$) according to the formula $N_{sig data} = N_{sig MC} \times (N_{CR data}/ N_{CR MC})$. This rescaling is not applied on the plots. We will clarify this procedure in the next update of this analysis.

2. Having the predictions from the other control regions in a table would have been nice to evaluate the statement that “CR2 and CR3 agree well with the background”.

   Yes you’re right, we will add these tables and the corresponding plots to the approved material for the next publication.

3. A distribution of the invariant mass of the bjet and lepton would be useful. This can show end points in spectra such as the top but also in potential signals. Any structure (or lack there of) in this variable is important to know.

   This plot can certainly be added to the approved material. However, we are looking at very busy final states and the huge combinatorics background could make difficult the interpretation of any structure (or lack of structure) in this variable.

4. Showing a distribution of the number of jets and the number of leptons would be helpful since many signals have high jet multiplicities and higher lepton multiplicities.

   We agree with you and we will also add these distributions to the approved material for the next publication.

5. There are several non-susy (simplified) models that would be potentially constrained by this analysis. For instance, Markus Luty has proposed:
   $g g \to A^0 \to W^\pm H^\mp \to W^\pm (W^\mp h^0) \to W^\pm (W^\mp (b \overline{b}))$ Comparing against wildly different models is interesting to see how sensitive the searches are to kinematics. Even one mass point showing the acceptance would be useful.

   Thanks for pointing us this interesting model. Generally, our policy consists in providing limits on simplified models plus model independent upper limits on the effective cross-section for new physics ($\sigma\times \text{efficiency}\times \text{acceptance}$) which can then be used by theorists to derive limits on their specific models. Thanks to many discussions ongoing between experimentalists and theorists, we will certainly improve the presentation of our results in the future to ease their exploitation by the theorists.

Forum: LHC - leptons + X – Topic: Discussion Session 11/3/11

The recent CMS multilepton analysis CMS PAS SUS-11-013

The discussion will be led by Can Kilic. Richard Gray, Sunil Somalwar and Scott Thomas (who are members of CMS involved in this analysis) will also join us to answer questions related to the analysis.

Forum: LHC - leptons + X – Topic: Discussion Session 10/27/11

Here is a summary of some of the issues that came up during the talk.

1. On charge misreconstruction, there was some discussion on whether it was a good approximation to apply a simple reweighting (by a single constant factor), when the discrepancy in figure 14 seemed to be dependent on $M_{ee}$. Another question was whether it would help to restrict to $\mid \eta \mid <1$, as the charge misreconstruction is much smaller there. In the end, since electron misreconstruction backgrounds are expected to be small, the first issue doesn’t affect the end result and it would hurt in signal statistics if the analysis went more central without a gain in signal to background.
2. There is interest in seeing more information about their events. Distributions in lepton and jets would be useful in certain models, but also as a check that the background modeling is understood. Overall, their analysis seems to be very inclusive, so any more detailed information is useful. However, their data-driven methods may have issues with finer distributions, as they become statistics limited.
3. Given that CMS very nicely gave parametrized efficiencies for detector level leptons and $H_T$, $E_T^{\mathrm{miss}}$, it would be useful to apply this to constrain other models, such as Little Higgs. Currently, there is only the CMSSM analysis in the paper and a simplified model of gluino pair production, decaying into $q\overline{q}{\chi }^{+}$, where ${\chi }^{+}\to {\chi }_0\ell \nu$.

Forum: General – Topic: Upcoming Talk Schedule

10/13/11: Jay Wacker will lead a discussion on “Search for supersymmetry in pp collisions at √s = 7 TeV in final states with missing transverse momentum, b-jets and one lepton with the ATLAS detector”. Forum link

10/27/11: Paddy Fox will lead a discussion will be on the CMS search for new physics in the same sign dilepton + missing energy final state. A link to the CMS note is provided on our forum website under the leptons+X section link.

11/03/11: Seminar on CMS multilepton (>=3) search, led by Can Kilic, with Rutgers CMS collaboration members (Richard Gray, Sunil Somalwar and Scott Thomas) available for questions and answer.
Forum link

11/17/11: Arjun Menon (U. Oregon) will be leading the discussion on the h->gamma gamma analysis (CMS-PAS-HIG-11-021).

Forum: LHC - leptons + X – Topic: Discussion Session 10/27/11

CMS-PAS-SUS-11-010: Search for new physics with same-sign isolated dilepton events with jets and missing energy

Discussion led by Patrick Fox at

Analysis is at paper link

Forum: LHC - leptons + X – Topic: Discussion Session 10/13/11

Are there are any comments related to last week’s forum on ATLAS-CONF-2011-130?

I had the following questions/comments:

1. How are the background normalizations taken? Did they really just use ALPGEN straight from the can to get the W/Z+jets backgrounds?
2. Markus pointed out the topology $p p \to Z' \to H h \to (b \overline{b}) (W W)$ and various other topologies. Markus, did you have a paper or note to reference?
3. Any other questions??

Forum: General – Topic: Feedback

Please give us any feedback on the forum or seminars. In particular, suggestions for improvements or things that are working well, be sure to let us know in this topic or in private communication with any of the organizers.

Forum: General – Topic: Technical Details

This topic is meant to provide helpful information to deal with technical issues related to the interactive forum sessions or with features of this website.

Forum: General – Topic: Sandbox

Some helpful information related to drawing wiggly lines in the above example:

In the slide-out drawer, next to the stroke-color and stroke-thickness controls, are a series of other controls, one of which gives you dashed (etc) strokes.

The wiggly line can be drawn as a path, with anchor points located, at regular intervals, along a line (easy, if you turn on the grid background), with slopes of equal magnitude, alternating in sign (again, easy to do, if you use the grid).

Forum: General – Topic: Sandbox

Integrated vector-graphics drawing program with TeX support.

Forum: LHC - leptons + X – Topic: Discussion Session 10/13/11

The link to the ATLAS note is here

Forum: General – Topic: Sandbox

Inline link:

Forum: General – Topic: Sandbox

Inline Tex:

Forum: LHC - leptons + X – Topic: Discussion Session 10/13/11

Search for supersymmetry in pp collisions at √s = 7 TeV in final states with missing transverse momentum, b-jets and one lepton with the ATLAS detector

Discussion led by Jay Wacker