Test of lepton flavour violation at the LHC

Neutralino dark matter in supersymmetric models is revisited in the presence of flavor violation in the soft supersymmetry breaking sector. We focus on flavor violation in the sleptonic sector and study the implications for the co-annihilation regions. Flavor violation is introduced by a singleμ R −τ R insertion in the slepton mass matrix. Limits on this insertion from BR(τ → µ + γ) are weak in some regions of the parameter space where cancellations happen within the amplitudes. We look for overlaps in parameter space where both the co-annihilation condition as well as the cancellations within the amplitudes occur. In mSUGRA, such overlap regions are not existent, whereas they are present in models with non-universal Higgs boundary conditions (NUHM). The effect of flavor violation is two fold: (a) it shifts the co-annihilation regions towards lighter neutralino masses (b) the co-annihilation cross sections would be modified with the inclusion of flavor violating diagrams which can contribute significantly. Even if flavor violation is within the presently allowed limits, this is sufficient to modify the thermally averaged cross-sections by about (10-15)% in mSUGRA and (20-30)% in NUHM, depending on the parameter space. In the overlap regions, the flavor violating cross sections become comparable and in some cases even dominant to the flavor conserving ones. A comparative study of the channels is presented for mSUGRA and NUHM cases.

Section: Discussionmentioning

confidence: 99%

Flavored co-annihilations

Chowdhury

Garani

Vempati

2012

“…The SU(2) × U(1) gauge invariant operators of equation (2.3) induce both D γ and D Z , 5 A could be suppressed with respect to C if the loop particles do not couple to the Higgs, but this does not suppress D couplings. 6 The operators inducing A coefficients also induce flavour-changing four fermion operators involving neutrinos. These are refered to as "Non-Standard neutrino Interactions", and can appear linearly in probabilities.…”

Section: Jhep09(2012)092mentioning

confidence: 99%

“…In this paper, we are interested in the prospects of Lepton Flavour Violating processes at the LHC, involving SM particles. LFV in BSM scenarios, such as supersymmetry or heavy singlet neutrinos, has received more attention [1][2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

LHC sensitivity to lepton flavour violating Z boson decays

Davidson

Lacroix

Verdier

2012

We estimate that the LHC could set bounds BR(Z → µ ± e ∓ ) < 4.1 × 10 −7 and BR(Z → τ ± µ ∓ ) < 3.5 × 10 −6 (at 95% C.L.) with 20 fb −1 of data at 8 TeV. A similar sensitivity can be anticipated for Z → τ ± e ∓ , because we consider leptonic τ decays such that Z → τ ± µ ∓ → e ± µ ∓ + invisible. These limits can be compared to the LEP1 bounds of order 10 −5 → 10 −6 . Such collider searches are sensitive to a flavour-changing effective Z coupling which is energy dependent, so are complementary to bounds obtained from τ → ℓlℓ and µ → eēe.

“…Concerning the former possibility, LFV could show up at the LHC in, e.g., neutralino decays, such as JHEP08(2010)133 83,84,91,[124][125][126][127][128], orχ 0 1 → ℓ ±l∓ 1 with ℓ = τ [129]. Moreover, since LFV also affects lepton-slepton-gravitino couplings [130], a small fraction of NLSP decaysl 1 → ℓG could produce a lepton ℓ = τ [131].…”

Section: Lepton Flavour Violationmentioning

confidence: 99%

Beyond the standard seesaw: neutrino masses from Kähler operators and broken supersymmetry

Brignole

Joaquim

Rossi

2010

We investigate supersymmetric scenarios in which neutrino masses are generated by effective d = 6 operators in the Kähler potential, rather than by the standard d = 5 superpotential operator. First, we discuss some general features of such effective operators, also including SUSY-breaking insertions, and compute the relevant renormalization group equations. Contributions to neutrino masses arise at low energy both at the tree level and through finite threshold corrections. In the second part we present simple explicit realizations in which those Kähler operators arise by integrating out heavy SU(2) W triplets, as in the type II seesaw. Distinct scenarios emerge, depending on the mechanism and the scale of SUSY-breaking mediation. In particular, we propose an appealing and economical picture in which the heavy seesaw mediators are also messengers of SUSY breaking. In this case, strong correlations exist among neutrino parameters, sparticle and Higgs masses, as well as lepton flavour violating processes. Hence, this scenario can be tested at highenergy colliders, such as the LHC, and at lower energy experiments that measure neutrino parameters or search for rare lepton decays.