Search for Noncommutative Microscopic Black Holes at the LHC
KINGSLEY EMELIDEME DEPARTMENT OF PHYSICS UNIVERSITY OF ALBERTA Micro Black holes? 2
A black hole is a region of space in which the pull of gravity is so strong that nothing can escape.
In the case of a micro black hole, strong gravity at small scales.
Consider partons (quarks and gluons) with the centre-of-mass energy √s = 푀퐵퐻 colliding head-on. If the impact parameter of the collision is less than the Schwarzschild radius 푅푆, a black hole with the mass 푀퐵퐻 is formed. Once produced, micro black holes would decay thermally via Hawking radiation, democratically to all Standard Model degrees of freedom. Noncommutativity Theory 3
Space time coordinates as noncommuting operators:
Noncommutativity provides a black hole with a minimum scale θ, known as the noncommutative black hole.
A point like distribution is no longer a Dirac delta, but a Gaussian
whose width coincides with θ = 1/Λ푁퐶,
Solving for spherically symmetric and static metric
Corresponding mass distribution is given by
Picking a random choice of 휃푀퐷= 0.6, we solved for gravitational radius and mass of black hole within our collider energy reach. Fundamental particles & forces 4
The universe as we know today contains less than 5% of matter.
Matter is made up of 12 basic building blocks called fundamental particles, governed by 4 fundamental forces.
Our best understanding of how these 12 particles and 3 forces are related is encapsulated in the so-called Standard Model.
Where is the gravitational force? Hierarchy Problem 5
Why is gravity some 1038 orders of magnitude weaker than other forces of nature?
Introducing the concept of 푛 extra dimensions in space (ADD), this hierarchy was alleviated.
By lowering the Planck scale from ~1016 TeV to ~1 TeV.
Referring to this reduced fundamental Planck scale as 푀퐷. Only gravity is allowed to propagate in extra dimension.
A consequence of low-scale (∼1TeV) quantum gravity in ADD model is production of microscopic black holes at colliders like the Large Hadron Collider (LHC). The LHC and the ATLAS Detector 6 The Large Hadron Collider (LHC) is a gigantic particle accelerator – the world’s biggest machine. Built in a circular tunnel 27 km in circumference and 100 m beneath the Swiss – French border.
ATLAS, which stands for A Toroidal LHC ApparatuS, is a general purpose experiment at the LHC. It has a length of 44 m with a diameter of 22 mm. Searching for NC black holes 7
Using ATLAS Datasets.
Background Monte Carlo :
QCD, W/Z + jets and 푡푡
Signal Monte:
n = 4, 푀퐷 = 0.94 TeV, remnant mass = 3.6 TeV – Modified Charybdis [Gingrich] NC black hole properties 8 Decay is democratic with quarks and gluons dominating, followed by leptons and higgs.
Events will have high multiplicity with soft 푝푇 jets. Leaves a remnant mass after decay. Cleaning & Selection of objects 9
Select data passing selected trigger.
Clean data for known detector problems like non-collisions and cosmic backgrounds using ATLAS standard cleaning criteria.
Determine efficiency of the selected trigger.
Trigger fully efficient at 140 GeV MET value.
푁푗푒푡 (푝푇 > 70 GeV && | 휂 < 2.8) Distribution of multiplicity 10 1푠푡 Distribution of 푝푇 after 푁푗푒푡 11 Distribution of ∑푝푇 after 푁푗푒푡 12 Background reduction 13
In order to optimize signal yield while reducing the background, we look for uncorrelated properties in the following combination. 1푠푡 ∑푝푇 versus 푝푇 . 1푠푡 푚푖푠푠 푝푇 versus 퐸푇 . 푚푖푠푠 ∑푝푇 versus 퐸푇 . Using these combinations of plots, we observe uncorrelated relationship between the: 1푠푡 푚푖푠푠 푝푇 versus 퐸푇 푚푖푠푠 ∑푝푇 versus 퐸푇 as shown on the next slides Use kinematic variables that are uncorrelated to derive cuts for background reduction. 1푠푡 14 Distribution of ∑푝푇 versus 푝푇 [1] ATLAS data QCD 1푠푡 푚푖푠푠 15 Distribution of 푝푇 versus 퐸푇 [2] ATLAS data QCD 푚푖푠푠 Distribution of ∑푝푇versus 퐸푇 [3] 16 ATLAS data QCD Derived selection cuts 17 1푠푡 18 Distribution of 푝푇 after derived cut Distribution of ∑푝푇 after derived cut 19 Normalized events number 20
Monte samples normalized to integrated luminosity of 502 푝푏−1 with a factor, w = 퐿푢푚푖푑푎푡푎 휎푀퐶 푁푢푚푏푒푟 표푓 푀퐶 푒푣푒푛푡푠 Result 21
In order to observe any discovery in ATLAS, we follow the ATLAS definition of signal significance, 푃 = 푆/√퐵, where S and B are the number of signal and background events, respectively.
The criteria for discovery is 푃 > 5 and S ≥ 10 observed signal events. Summary 22 We considered experimental limits on the Planck scale and the energy reach of the LHC to calculate the production cross section for NC black holes.
BH search was conducted with a total luminosity of 502 푝푏−1 of ATLAS data with a centre of mass energy, √s = 7 TeV.
Our BH events have a cross-section, 휎 = 4.67 pb with: number of extra dimensions, n = 4, Planck scale, 푀퐷 = 0.94 TeV and remnant mass of 3.6 TeV.
The LHC may produce 526 black hole events with an integrated luminosity of of 502 푝푏−1. Despite a 푃 > 5 we can not claim discovery of a BH event in ATLAS since the total MC simulated background is less than the ATLAS data used. 23
THANK YOU FOR LISTENING Distribution of multiplicity after derived cut Noncommutative (NC) black holes
Solving for spherically symmetric and static metric.
where
Picking 휃푀퐷 = 0.6 1푠푡 Distribution of ∑푝푇 versus 푝푇 [1]
ATLAS data QCD 푡푡 1푠푡 Distribution of ∑푝푇 versus 푝푇 [2]
W + jets Z + jets 푡푡 1푠푡 푚푖푠푠 Distribution of 푝푇 versus 퐸푇 [2]
W + jets Z + jets Black Hole 푚푖푠푠 Distribution of ∑푝푇versus 퐸푇 [2]
W + jets Z + jets Black Hole ATLAS data cutflow 30 31