The Electroweak Sector of the pMSSM in the Light of LHC - 8 TeV and Other Data

Using the chargino-neutralino and slepton search results from the LHC in conjunction with the WMAP/PLANCK and $(g-2)_{\mu}$ data, we constrain several generic pMSSM models with decoupled strongly interacting sparticles, heavier Higgs bosons and characterized by different hierarchies among the EW sparticles. We find that some of them are already under pressure and this number increases if bounds from direct detection experiments like LUX are taken into account, keeping in mind the associated uncertainties. The XENON1T experiment is likely to scrutinize the remaining models closely. Analysing models with heavy squarks, a light gluino along with widely different EW sectors, we show that the limits on gluino mass are not likely to be below 1.1 TeV, if a multichannel analysis of the LHC data is performed. Using this light gluino scenario we further illustrate that in future LHC experiments the models with different EW sectors can be distinguished from each other by the relative sizes of the $n$-leptons + $m$-jets + ${\mbox{${E\!\!\!\!/_T}$}}$ signals for different choices of $n$.


Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

LHC searches
ATLAS searches are restricted for simplified models → where all sparticles except those relevant for the signal are taken to be decoupled.
When all strong sector sparticles are heavy (≃ TeV), direct production of chargino-neutralinos may be the dominant SUSY process.
χ ± 1 and χ 0 2 are taken to be mass-degenerate and purely wino .
Lightest neutralino is assumed to be predominantly bino.
All three generations of sleptons and sneutrinos are assumed mass degenerate.
Sneutrinos and sleptons are assumed to be mass degenerate with their masses lying midway between χ ± 1 and χ 0 1 .

Decay via gauge bosons
There can be decays via gauge bosons when sleptons are heavier than χ ± 1 / χ 0 2 .
ATLAS searches assume 100 % BR for the decay modes : BR for the decay mode χ 0 2 → h χ 0 1 is taken to be zero.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

Our analysis
Strong sector beyond LHC reach ⇒ all squark masses and CP-odd, heavy Higgs masses are taken to be decoupled.
Right and left slepton masses are placed in different relative positions in between M 1 and M 2 .
For models where sleptons are taken to be heavier than χ ± 1 , we take ml = M 2 + 200 GeV.
Sneutrino mass is calculated according to pMSSM mass relations : We use PYTHIA [version 6.4] for event generation using the selection criteria of ATLAS collaboration at the generator level.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

Indirect constraints
We try to constrain pMSSM parameter space with the help of following indirect constraints: WMAP/PLANCK relic density.
Spin independent direct detection data from XENON/LUX.
We also study indirect detection prospects of dark matter.
Indirect constraints : muon (g-2) One of the most precisely determined quantities of particle Physics.
SM contributions : QED, weak, hadronic vacuum polarization, hadronic light by light scattering.
Significant theoretical uncertainty in calculating hadronic contribution.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T Contribution from chargino-sneutrino and neutralino-smuon loop diagrams.
Contributions proportional to tanβ → can explain the anomaly.
In presence of light left-right sleptons neutralino-smuon loop can give significant contribution in pMSSM.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

DM relic density constraint
Some annihilation channels that could give right relic density : There can be coannihilations with sparticles of slightly heavier masses:

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T Relies on elastic scattering of LSP off nuclei in a detector : nuclear recoil energy is measured.
Interactions can be spin-dependent/independent.
Cross-section for scattering: Taking λ p ≃ λ n there is strong enhancement for large nuclei → σ SI 0 ∝ A 2 . SI interaction usually dominates SD ones for heavier nuclei.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

DM direct detection
Calculation of WIMP -nucleus interaction is a three-step process.
From WIMP-quark to WIMP -nucleon : nuclear matrix elements are required.
From WIMP-nuclear to WIMP-nucleon : Nuclear form factors are introduced.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

Sources of uncertainty
Nuclear matrix elements : ⇒ strangeness content of nucleon σ s = m s < p|ss|p > Local DM density, local DM velocity.
DM density profile and velocity distribution.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T SUSY diagrams for SI and SD scattering Diagrams contributing to SI interaction

Diagrams contributing to SD interaction
We would focuss on SI interaction :Since squarks are heavy in our case, Higgs exchange diagrams dominate.

Indirect detection
Signals from pair annihilation of LSP's in astrophysically dense regions like galactic core, dwarf galaxies etc.
Photons can come from final state radiation, decays and hadronization of the product of final state particles etc.
p-wave processes are velocity suppressed since v c ≃ 10 −3 in present universe.
s-wave processes are helicity suppressed.
As we take highly bino-dominated LSP ⇒ small annihilation cross-section.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T We study following models keeping slepton masses in different relative positions wrt chargino and neutralino : (1) Light Gaugino and Left Slepton (LGLS) Scenario : Left slepton mass is kept midway between chargino and neutralino by taking Ml L = 0.5M 1 + 0.5M 2 . Right sleptons are taken to be heavy. Tilted-LGLS scenario : Left slepton mass is placed more towards chargino or neutralino ⇒ x = 0.25/0.75 respectively. Right sleptons are taken to be heavy.

Light Gaugino and Left and Right Slepton (LGLRS) Scenario :
Left and right sleptons are mass-degenerate. Slepton mass is kept midway between chargino and neutralino.
Tilted-LGLRS scenario : Left and right slepton masses are placed more towards chargino or neutralino ⇒ x = 0.25/0.75 respectively.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

Models analyzed
We also study : In the left plot we reproduce ATLAS result by our simulation → small difference due to: → D-term contribution in sneutrino masses. → No detector simulation. Chargino-sneutrino loop contribution to muon (g-2) dominates. Relic density satisfying mechanism : sneutrino coannihilation for the upper branch. Z/h resonance for the lower branch.
For high tanβ muon (g-2) satisfied regions shift towards right : significant amount of parameter space left allowed by combined constraints.
No effect of increasing tanβ on collider sector.
Higgs-resonance region disappears for high tanβ at larger m e The leptons arising from decays of χ ± 1 / χ 0 2 would be softer. This reduces the trilepton efficiency and relaxes the LHC constraints.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T LGLRS scenario Since χ ± 1 and χ 0 2 are wino-dominated they decay mainly via left sleptons. Thus the inclusion of right sleptons has almost no effect on collider limit. Neutralino-smuon loop contribution to muon (g-2) is dominant. τ 1 is the NLSP. Stau coannihilation, Z/h resonance mechanisms in action. For higher tanβ Higgs resonance region disappears. The leptons arising from χ ± 1 / χ 0 2 decays would be softer. This reduces the trilepton efficiency and relaxes the LHC constraints.
For higher tanβ, in addition there is large mixing ⇒ stau lighter than selectron. This further reduces the efficiency.
LGHS scenario L and R sleptons are assumed mass degenerate and heavier than χ ± 1 / χ 0 2 . LGLS scenarios : heavy tanβ cases still allowed and to be probed by future XENON1T experiment.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T Black points allowed by combined constraints : still allowed by LUX.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T

What if gluino is within LHC reach ?
Gluino is the strong sparticle with the largest cross-section at LHC.
We try to see the effect of taking one strong sector sparticle within LHC reach on the EW sector. For the LGLS and LGLRS models gluino will decay to χ ± 1 / χ 0 2 which will decay further to leptons making leptonic signals stronger. For the LGHS scenario gluino decays viag → qq χ 0 1 making 0-lepton signal strongest.
Thus, it is possible to distinguish among different EW scenarios by looking at the gluino decays in the n leptons + jets + E / T channels with n = 0, 1, 2.
conclusion Direct LHC bounds on EW sector sparticles are rather weak. It is possible to constrain pMSSM parameter space with the help of indirect constraints along with direct collider limits. WMAP relic density data, muon (g-2) constraint and DM direct detection experiments can be very significant.
Some DM mechanisms like sneutrino coannihilation which are disfavored in mSUGRA type of scenarios are still allowed in PMSSM. h/Z resonance mechanisms, bulk annihilation are in tension even in pMSSM under combined constraints. Different EW scenarios can be distinguished if gluino remains within LHC reach.

Manimala Chakraborti
The Electroweak Sector of the pMSSM in the Light of LHC -8 T where f T G = 1 − u,d,s f (p) Tq . The second term comes from coupling of heavy quarks to gluons through trace anomalies The effective coupling between the neutralino and nucleon through the Higgs exchange, f H q , is given by BR(B s → µ + µ − ) SUSY ∝ tan 6 β ma 4