Constrained S^min\sqrt{\hat{S}_{min}} and reconstructing with semi-invisible production at hadron colliders

Mass variable \sqrt{\hat{S}_{min}} and its variants were constructed by minimising the parton level center of mass energy that is consistent with all inclusive measurements. They were proposed to have the ability to measure mass scale of new physics in a fully model independent way. In this work we relax the criteria by assuming the availability of partial informations of new physics events and thus constraining this mass variable even further. Starting with two different classes of production topology, i.e. antler and non-antler, we demonstrate the usefulness of these variables to constrain the unknown masses. This discussion is illustrated with different examples, from the standard model Higgs production and beyond standard model resonance productions leading to semi-invisible production. We also utilise these constrains to reconstruct the semi-invisible events with the momenta of invisible particles and thus improving the measurements to reveal the properties of new physics.Comment: v2: typos corrected, references added; Matches with published version. 22 pages, 14 figure

Reconstructing semi-invisible events in resonant tau pair production from Higgs

We study the possibility of utilising the constrained mass variable, $M_{2Cons}$, in reconstructing the semi-invisible events originated from a resonant production at the LHC. While this proposal is effective for any similar antler type production mechanism, here we demonstrate with potentially interesting scenario, when the Higgs boson decays into a pair of third generation $\tau$ leptons. Buoyed with a relatively large Yukawa coupling, the LHC has already started exploring this pair production to investigate the properties of Higgs in the leptonic sector. Dominant signatures through hadronic decay of tau, associated with invisible neutrinos compound the difficulty in the reconstruction of such events. Exploiting the already existing Higgs mass bound, this new method provides a unique event reconstruction, together with a significant enhancement in terms of efficiency over the existing methods.Comment: 14 pages, 3 figures; addition of text and footnote for further clarification, Figure 3 modified to append the further improvement of efficiency in selected events; version accepted for publication in Phys. Lett.

MT2M_{T2} as a probe of CP phase in h→ττh \rightarrow \tau \tau at the LHC

We propose to utilize the transverse mass variable $M_{T2}$ and it's descendant $M_{2Cons}$ for constraining the CP admixture of the tau lepton Yukawa coupling at the LHC. We have considered the tau lepton pair produced from the Higgs boson with each tau decays to a charged pion and a neutrino, $\tau^{\pm} \rightarrow \pi^{\pm} \nu_{\tau}$. Recently, for this channel, the LHC has employed the impact parameter method to measure the CP mixing angle of tau lepton Yukawa coupling with large uncertainty. The observables we propose here can be measured in the lab frame without the impact parameter measurement and in turn, give a complementary probe of the CP admixture of tau lepton Yukawa. The CP mixing angle, with our method, can be constrained up to 17$^{\circ}$ (7$^{\circ}$) with 300 (3000) $fb^{-1}$ of integrated luminosity at the 14 LHC.Comment: 14 pages, 4 figure

Sbottoms as probes to MSSM with nonholomorphic soft interactions

Presence of nonholomorphic soft SUSY breaking terms is known to be a possibility in the popular setup of the Minimal Supersymmetric Standard Model (MSSM). It has been shown that such a scenario known as NonHolomorphic Supersymmetric Standard Model (NHSSM) could remain `natural' ( i.e., not fine-tuned) even in the presence of a rather heavy higgsino-like LSP. However, it turns out that distinguishing such a scenario from the MSSM is unlikely to be an easy task, in particular at the Large Hadron Collider (LHC). In a first study of such a scenario at colliders (LHC), we explore a possible way that focuses on the sbottom phenomenology. This exploits the usual $\tan\beta$-dependence (enhancement) of the bottom Yukawa coupling but reinforced/altered in the presence of non-vanishing nonholomorphic soft trilinear parameter $A_b^{\prime}$. For a given set of masses of the sbottom(s) and the light electroweakinos (LSP, lighter chargino etc.) which are known from experiments, the difference between the two scenarios could manifest itself via event rate in the 2b-jets + ${\, \not \! \! E_T}$ final state, which could be characteristically different from its MSSM expectation. Impact on the phenomenology of the stops at the LHC is also touched upon.Comment: 32 pages, 17 figures, 1 table, no changes in texts/figures, three references added, version published in JHE

Towards efficient reconstruction of semi-invisible events from higgs at the LHC

by Akanksha Bhardwaj, Partha Konar and Abhaya Kumar Swai

Measuring

The proposed future $$e^- p$$ collider provides sufficient energies to produce the Standard Model Higgs Boson (h) through $$W^\pm$$ and Z-Boson fusion in charged and neutral current modes, respectively and to measure its properties. We take this opportunity to investigate the prospect of measuring the CP properties of h through $$h \rightarrow \tau ^{+} \tau ^{-}$$, where $$\tau ^{-}\,\left( \tau ^{+}\right)$$ decays to a charged pion $$\pi ^-\,\left( \pi ^+\right)$$ and a neutral pion $$\pi ^0$$ in association with neutrino (anti-neutrino). An interesting CP sensitive angular observable $$\alpha _{\mathrm{CP}}$$ between the two $$\tau$$-leptons decay plane in the $$\pi ^+\pi ^-$$ centre of mass frame is proposed and investigated in this work. For fixed electron energy of 150 GeV along with 7 (50) TeV of proton energy, the CP phase can be measured approximately to $$25^\circ$$ ($$14^\circ$$) at integrated luminosity of 1 ab$$^{-1}$$ for −80% polarised electron at 95% confidence level