The MasterCode Project

News

The pMSSM10 prior to LHC RUN II [Apr 13, 2015]

We present a frequentist analysis of the parameter space of the pMSSM10, in which the following 10 soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale Msusy = Sqrt[M_stop1 M_stop2]: the gaugino masses M_{1,2,3}, the 1st-and 2nd-generation squark masses M_squ1 = M_squ2, the third-generation squark mass M_squ3, a common slepton mass M_slep and a common trilinear mixing parameter A, the Higgs mixing parameter mu, the pseudoscalar Higgs mass M_A and tan beta. We use the MultiNest sampling algorithm with 1.2 x 10^9 points to sample the pMSSM10 parameter space. A dedicated study shows that the sensitivities to strongly-interacting SUSY masses of ATLAS and CMS searches for jets, leptons + MET signals depend only weakly on many of the other pMSSM10 parameters. With the aid of the Atom and Scorpion codes, we also implement the LHC searches for EW-interacting sparticles and light stops, so as to confront the pMSSM10 parameter space with all relevant SUSY searches. In addition, our analysis includes Higgs mass and rate measurements using the HiggsSignals code, SUSY Higgs exclusion bounds, the measurements B-physics observables, EW precision observables, the CDM density and searches for spin-independent DM scattering. We show that the pMSSM10 is able to provide a SUSY interpretation of (g-2)_mu, unlike the CMSSM, NUHM1 and NUHM2. As a result, we find (omitting Higgs rates) that the minimum chi^2/dof = 20.5/18 in the pMSSM10, corresponding to a chi^2 probability of 30.8 %, to be compared with chi^2/dof = 32.8/24 (31.1/23) (30.3/22) in the CMSSM (NUHM1) (NUHM2). We display 1-dimensional likelihood functions for SUSY masses, and show that they may be significantly lighter in the pMSSM10 than in the CMSSM, NUHM1 and NUHM2. We discuss the discovery potential of future LHC runs, e+e- colliders and direct detection experiments.

The SLHA files of our benchmark points can be obtained from here: Full text at arXiv:1504.03260 [hep-ph].

The CMSSM and NUHM1 after LHC Run 1 [Dec 18, 2013]

We analyze the impact of data from the full Run 1 of the LHC at 7 and 8 TeV on the CMSSM with μ>0 and μ<0 and the NUHM1 with μ>0, incorporating the constraints imposed by other experiments such as precision electroweak measurements, flavour measurements, the cosmological density of cold dark matter and the direct search for the scattering of dark matter particles in the LUX experiment. We use the following results from the LHC experiments: ATLAS searches for events with MET accompanied by jets with the full 7 and 8 TeV data, the ATLAS and CMS measurements of the mass of the Higgs boson, the CMS searches for heavy neutral Higgs bosons and a combination of the LHCb and CMS measurements of Bs→μμ and Bd→μμ.

Full text at arXiv:1312.5250 [hep-ph].

Supersymmetry in light of LUX [October 31st, 2013]

On October 30th the LUX Collaboration announced the first results of its direct search for spin-independent WIMP dark matter scattering on Xenon, which are significantly more sensitive than previous such experiments, particularly in the region of low WIMP masses. We present here some preliminary results from a global analysis of the parameter spaces of simple supersymmetric models in light of LUX.

These results also incorporate the (negative) results of ATLAS searches for events with jets and missing transverse energy at the LHC with ∼20/fb of luminosity at 8 TeV, as well as the CMS and LHCb measurements of Bs→μμ decay. We also include the implications for supersymmetric models of the measurements by the ATLAS and CMS Collaborations of the mass of the Higgs boson, as interpreted using the latest version of the FeynHiggs code, which yields an improved calculation leading to somewhat larger light Higg boson masses than previous versions for the same values of the supersymmetric model input parameters.

figure figure
The (mχpSI) planes in the CMSSM (left panel) and the NUHM1 (right panel). The Δχ2 = 2.30(5.99) contours, corresponding to the 68(95)% CL are coloured red (blue). The solid (dashed) lines are for global fits including (excluding) the new LUX results. The new best-fit points are indicated by a solid green star. The 90% CL exclusion lines of LUX and XENON100 are also shown. Note that the global fit contours include an additional systematic uncertainty on σpSI.

Implications of the first evidence of the Bs→μμ decay! [November 12, 2012]

After the publication of the first measurement of the Bs→μμ branching fraction by the LHCb experiment, we update our frequentist analysis of the parameter space of the CMSSM and NUHM1 models. The following results are based on a (non-official) combination of the ATLAS, CDF, CMS, and LHCb results yielding: BR(Bs→μμ) ≈ 3.0-1.1+1.2 x 10-9.

The new measurement provides a valuable new constraint on the supersymmetric parameter space, but the observation of a Standard Model-like branching fraction for the Bs→μμ decay is quite consistent with supersymmetry. In fact, a Standard Model-like branching fraction of this decay was expected in constrained supersymmetric models like the CMSSM or NUHM1 (see, e.g., the recent MasterCode results for further details).

As a result, the favoured regions in the parameter space of these models do not change significantly after the inclusion of the new constraint.

figure
Combination of BR(Bs→μμ) measurements: ATLAS (cyan, Winter 2012), CDF (dark blue, ASPEN 2012), CMS (red, Winter 2012), LHCb (blue, HCP 2012). The combined likelihood is shown in green.


figure figure
Prediction for BR(Bs→μμ) in the (m0,m1/2) plane, in the (left) CMSSM and (right) NUHM1 models. The red (blue) contour shows the 68% (95%) C.L. exclusion, after including the already published constraints from the LHC and XENON100, as well as the new LHCb result.
figure figure
68% and 95% C.L. contours in the (m0,m1/2) plane, in the (left) CMSSM and (right) NUHM1 models. The dashed lines include the already published constraints from the LHC and XENON100, the solid lines include the new LHCb result in addition.


figure figure
Prediction for BR(Bs→μμ) in the (MA,tanβ) plane, in the (left) CMSSM and (right) NUHM1 models.


figure figure
68% and 95% C.L. contours in the (MA,tanβ) plane, in the (left) CMSSM and (right) NUHM1 models.


figure figure
Δχ2 distributions for BR(Bs→μμ) normalized to SM expectation in the (left) CMSSM and (right) NUHM1 models, after (solid line) and before (dashed line) the new LHCb result.


figure figure
Δχ2 distributions for the gluino mass in the (left) CMSSM and (right) NUHM1 models, after (solid line) and before (dashed line) the new LHCb result.

Grand summary of 2011 searches [Summer 2012]

We make a frequentist analysis of the parameter space of the CMSSM and NUHM1, using a Markov Chain Monte Carlo (MCMC) with 95 (221) million points to sample the CMSSM (NUHM1) parameter spaces.

Our analysis includes the ATLAS search for supersymmetric jets + MET signals using ∼5/fb of LHC data at 7 TeV, which we apply using PYTHIA and a Delphes implementation that we validate in the relevant parameter regions of the CMSSM and NUHM1.

Our analysis also includes the constraint imposed by searches for Bs→μμ by LHCb, CMS, ATLAS and CDF, and the limit on spin-independent dark matter scattering from 225 live days of XENON100 data.

We assume M_h ∼ 125 GeV, and use a full set of electroweak precision and other flavour-physics observables, as well as the cold dark matter density constraint.

The ATLAS 5/fb constraint has relatively limited effects on the 68 and 95% CL regions in the (m_0, m_1/2) planes of the CMSSM and NUHM1. The new Bs→μμ constraint has greater impacts on these CL regions, and also impacts significantly the 68 and 95% CL regions in the (M_A, tanβ) planes of both models, reducing the best-fit values of tanβ. The recent XENON100 data eliminate the focus-point region in the CMSSM and affect the 68 and 95% CL regions in the NUHM1.

In combination, these new constraints reduce the best-fit values of m_0, m_1/2 in the CMSSM, and increase the global χ2 from 31.0 to 32.8, reducing the p-value from 12% to 8.5%. In the case of the NUHM1, they have little effect on the best-fit values of m_0, m_1/2, but increase the global χ2 from 28.9 to 31.3, thereby reducing the p-value from 15% to 9.1%.

More information:
→ The CMSSM and NUHM1 in Light of 7 TeV LHC, Bs→μ+μ- and XENON100 Data

New results including 1/fb of LHC data [October 11, 2011]

We update previous frequentist analyses of the CMSSM and NUHM1 parameter spaces to include the public results of searches for supersymmetric signals using ~1/fb of LHC data recorded by ATLAS and CMS and ~0.3/fb of data recorded by LHCb in addition to electroweak precision and B-physics observables. We also include the constraints imposed by the cosmological dark matter density and the XENON100 search for spin-independent dark matter scattering.

The LHC data set includes ATLAS and CMS searches for jets + missing ET events and for the heavier MSSM Higgs bosons, and the upper limits on Bs→μμ from LHCb and CMS. The absences of jets + missing ET signals in the LHC data favour heavier mass spectra than in our previous analyses of the CMSSM and NUHM1, which may be reconciled with (g-2)μ if tanβ ~40, a possibility that is however under pressure from heavy Higgs searches and the upper limits on Bs→μμ. As a result, the p-value for the CMSSM fit is reduced to ~15 (38)%, and that for the NUHM1 to ~16 (38)%, to be compared with ~9 (49)% for the Standard Model limit of the CMSSM for the same set of observables (dropping (g-2)μ), ignoring the dark matter relic density in both cases.

We discuss the sensitivities of the fits to the (g-2)μ and b→sγ constraints, contrasting fits with and without the (g-2)μ constraint, and combining the theoretical and experimental errors for b→sγ linearly or in quadrature. We present predictions for mgluino, Bs→μμ, Mh and MA, and update predictions for spin-independent dark matter scattering, stressing again the importance of taking into account the uncertainty in the pi-nucleon sigma term, ΣπN. Finally, we present predictions based on our fits for the likely thresholds for sparticle pair production in ee collisions in the CMSSM and NUHM1.

More information:
→ Supersymmetry in Light of 1/fb of LHC Data
→ A selection of results

MasterCode's "red band plots" on the front page of EPJC! [September 6, 2011]

A figure of our most recent paper, displaying the prediction for the lightest Higgs mass in various constrained versions of the MSSM, was selected as a cover picture for EPJC vol. 71, no. 8. figure

EPS 2011 update

The ATLAS and CMS Collaborations have recently presented at the EPS conference in Grenoble (http://eps-hep2011.eu/) new results from more powerful all-hadronic SUSY searches, using about 1/fb of 2011 LHC data. (http://eps-hep2011.eu/) new results of their powerful all-hadronic SUSY searches: In addition, the CMS, LHCb, and CDF Collaborations have also presented stringent new limits on the branching fraction for the Bs→μμ decay: Here we incorporate this new information in an update of our recent frequentist global analysis of the parameter spaces of the CMSSM and NUHM1: arXiv:1106.2529 [hep-ph].

In that reference we incorporated a combination of the Bs→μμ constraints from LHCb and D0, and also the previous CDF constraint, as well as the available LHC 2010 and XENON100 constraints, as well as other observables including the LEP Higgs limit, b→sγ decay, gμ-2, the relic cold dark matter density, precision electroweak observables. Details of our analysis can be found there.

In the absences of official combinations of the new limits, we use in each case the single most constraining limit. For the all-hadronic searches we use the CMS result up to m0 = 1 TeV and the ATLAS limit for m0 > 1 TeV. In case of BR(Bs→μμ) we use the limit from LHCb.

We display first the (m0, m1/2) planes of the CMSSM (Figure 1) and NUHM1 (Figure 2), showing best-fit points (green stars), 68% CL boundaries (red lines) and 95% CL boundaries (blue lines). The dotted (solid) lines are before (after) including the new constraints presented at EPS. To further illustrate the impact of the new limits on the allowed parameter space, we also show in the same plotting format the correlation of the spin-independent dark matter scattering cross section with the mass of the lightest supersymmetric particle (neutralino) in these models (Figure 3 CMSSM and Figure 4 NUHM1).

In both models, the best-fit point changes significantly due to the tight constraints from the new direct all-hadronic SUSY searches. The overall χ2 increases from 26.2 to 30.2 in the CMSSM and from 24.2 to 27.0 in the NUHM1, yielding a χ2-probability of about 11% for the CMSSM and 17% for NUHM1.

Figure 1: The (m0,m1/2) plane of the CMSSM showing best-fit points (green stars), 68% CL boundaries (red lines) and 95% CL boundaries (blue lines). The dotted (solid) lines are before (after) including the new constraints presented at EPS. figure
Figure 2 : The (m0,m1/2) plane of the NUHM1 showing best-fit points (green stars), 68% CL boundaries (red lines) and 95% CL boundaries (blue lines). The dotted (solid) lines are before (after) including the new constraints presented at EPS. figure
Figure 3: Correlation of the spin independent cross section with the mass of the neutralino of the CMSSM showing best-fit points (green stars), 68% CL boundaries (red lines) and 95% CL boundaries (blue lines). The dotted (solid) lines are before (after) including the new constraints presented at EPS. figure
Figure 4: Correlation of the spin independent cross section with the mass of the neutralino of the NUHM1 showing best-fit points (green stars), 68% CL boundaries (red lines) and 95% CL boundaries (blue lines). The dotted (solid) lines are before (after) including the new constraints presented at EPS. figure
The tension on the parameter space of these constrained SUSY models is more visible when displaying the χ2-probability in (m0,m1/2) planes. As can be seen in Figure 5, the CMSSM still exhibits a rather large region in the parameter space with a goodness of fit probability of better then 5% (green region) but since the best fit probability is only 11%, overall the portion of parameter space of this model still allowed possesses only rather a low chi2 probability, as given above. The situation is slightly better in the case of the less constrained NUHM1 (Figure 6), but also here the overall probability of 17% is also significantly lower than before the EPS conference.
Figure 5: The χ2 probability of the CMSSM displayed in the (m0,m1/2) plane. The green contour contains the parameter space region with a probability of 5% or higher. The best-fit probability is 11%. figure
Figure 6: The χ2 probability of the NUHM1 displayed in the (m0,m1/2) plane. The green contour contains the parameter space region with a probability of 5% or higher. The best-fit probability is 17%. figure
Finally, we display the 1-dimensional χ2 functions for Bs→μμ in the CMSSM (in green, Figure 7) and NUHM1 (in purple, Figure 8), showing the pre- (post-)EPS predictions as dotted (solid) lines.
Figure 7: Δχ2 distribution for BR(Bs→μμ)/SM in the CMSSM model. figure
Figure 8: Δχ2 distribution for BR(Bs→μμ)/SM in the NUHM1 model. figure
We await with interest the results on the combination of Bs→μμ results and will update arXiv:1106.2529 [hep-ph] more fully at that time. The update will also discuss the impacts of different treatments of the gμ-2 and b→sγ constraints on global fits.
visits - Last modified: Tue 14 Apr 2015