m.savina, november 25, npd ras 2009 1 black hole production at the lhc: peculiarities, problems,...

M.Savina, November 25, NPD RAS 2009M.Savina, November 25, NPD RAS 2009 11

Black Hole Production at the LHC:peculiarities, problems, expectations

Savina MariaJINR, Dubna

22M.Savina, November 25, NPD RAS 200M.Savina, November 25, NPD RAS 20099

Part I. Optimistic Symphony – The Old PredictionsPart I. Optimistic Symphony – The Old Predictions

• D-dimensional (D>4) models – possible realizations of TeV-scale gravity

• BH in D dimensions: formation, decay, experimental expectations

• Predictions for the LHC, event generators for BH production, benefits and limitations

•


Black Hole formation in TeV-scale gravityBlack Hole formation in TeV-scale gravity

Pictures by Sabine Hossenfelder

In large extra dimension models• Gravity stronger at small distances• Horizon radius larger• For M ~ TeV it increases to 10-4 fm For these BH Rh<< R and they have approximately higher dimensional sphericalsymmetry

At the LHC partons can come closer than their Schwarzschild horizon

a black hole production


BH Production in pp collisions: some well-known formulas BH Production in pp collisions: some well-known formulas

Schwarzschild raduis of a multidimensional BH(as given by R. Meyers, M. Perry)

BH production cross section

Differential BH production cross section

PDF’s


BH Production in pp collisions at the LHCBH Production in pp collisions at the LHC

Increasing cross section, no suppression from small couplings


Hawking evaporation of BHHawking evaporation of BH

Hawking temperature

where

Multiplicity of produced particles in BH decay


Grey Body Factors for BH Decay Grey Body Factors for BH Decay

Grey body factors

# D.o.F. for e- # D.o.F. for GB


Entropy, BH decay and Entropy, BH decay and MMminmin(BH)(BH)

BH Entropy

Democratic decay blinded to flavor: probabilities are the same for all species (violation of some conservation laws)

The ratio of hadronic/leptonic is 5 : 1

SBH must be large enough to reproduce thermal BH decay

SBH > 25


BH Production in pp collisions at the LHCBH Production in pp collisions at the LHC

DL ‘01

For the LHC energies:

a) Parton-level productioncross section

b) Differential cross section

c) Hawking temperature

d) Average decay multiplicityfor Schwarzschild BH

n=4


Black Hole or String Ball?Black Hole or String Ball?

MBH >> MD : semiclassical well-known description for BH’s.

What happens when MBH approach MD?BH becomes “stringy”, their properties become complex.


Black Hole vs String Ball ProductionBlack Hole vs String Ball Production

Matching: smooth transition between two regimes

Production cross section:


Production cross section for BH, SB and p-braneProduction cross section for BH, SB and p-brane


Final state of the SM process vs typical BH decay spectraFinal state of the SM process vs typical BH decay spectra

Multi-jet and hard leptons events, spherical, typical temperature about 200 GeV

Pictures by Sabine Hossenfelder

SM BH decay


BH Experimental SignaturesBH Experimental Signatures

• Potentially large cross sections, approaching 103 fm or more

• An increase of cross sections with energy, according to an absense of gauge coupling suppression (will be hard to see at the LHC)

• Relatively high sphericity for final states

• High multiplicity as proportional to the BH entropy of particles produced (primaries)

• Hard trasverse leptons an jets, in significant numbers

• Approximately thermally determined ratios of species (democratic decay)

• Suppression of highest-energy jets

• Decrease of decay primary (lepton/parton) energy with total event transverse energy (resulting from decreasing Hawking temperature with mass)


BH Production GeneratorsBH Production Generators

TRUENOIR

CHARYBDIS (C.M. Harris, P. Richardson, B.R. Webber ’03)

The very first BH generator. Conservation of baryon and lepton numbers, QCD colors. Rapid decay approximation. No GBF, temperature variation during Hawking stage, no spindown phase

In use in collaborations now. More progressive than Truenoir. Proper to Les Houches format event convention.GBF, temperature evolution during thernal phase, two choices of PDF scale,Number of remnants in Planck phase

As earlier: No simulation for spindown phase and old results for entropy (underestimation of BH lifetime and some differences in Multiplicities of primery produced particles)

Up to now we have no correct BH generator, in which all stages of BH evolution would be included !!


CHARIBDISCHARIBDIS ParametersParameters


CHARYBDIS Simulation ResultsCHARYBDIS Simulation Results

w/o temp. variation

w/o GBF

M=5.0-5.5 TeV

Higgs boson spectrum

Electron and Positronspectra


CHARYBDIS Simulation ResultsCHARYBDIS Simulation Results

Effects from remnants at the end of Planck stage: w /wo


CHARYBDIS Gen.: Analysis and results for the CMS CHARYBDIS Gen.: Analysis and results for the CMS

M_recSphericity

CMS PTDR Vol. II, 2007

Hard jets, leptons and γ’s

L = 30 fb-1

As a benchmark:2 TeV/c2 fundamental Planck scale4 TeV/c2 – 14 TeV/c2 BH massn=3 number of ED


CHARYBDIS Gen.: Analysis and results for the CMSCHARYBDIS Gen.: Analysis and results for the CMS

Event selection:

• The total pT of all reconstrected objects plus missing ET is larger then 2500 GeV• Level-1 and HLT trigger included• 4-jet trigger (with 93 % efficiency)

The CMS mass reach:For L = 10 – 100 pb -1 and MD = 2 – 3 TeV Mmin(BH) up to 4 TeV and n = 2 – 6.


Optimistic Resume:

• BH wil be produced at the LHC with enormous rate up to about 1 KHz (for L = 100 fb-1)

• BH is spectacular clear experimental signature: a “fireball” decay, spherically symmetric, large multiplicity of hard jets, leptons, photons, thermal “democratic” spectra

• BH production may be the very first evidence for the ED (much earlier then KK modes and missing energy signals from different ED models) because its huge rate.


Part II. Optimism Is fading…Part II. Optimism Is fading…

BH not as spectacular as advertized!!

• BH Production near the threshold and careful counting

• Conventions on a fundamental mass

• Inelasticity for BH formation at the LHC and in the UHECR

• Minimal M for a sensible definition of a BH

• LHC unlikely to make classical BH with thermal decay spectra. So, what can we see, then?

• Two-body final states and QG

… … but it is not the end of the storybut it is not the end of the story


L. Randall’s Talk at String’07:


Conventions on a fundamental mass Conventions on a fundamental mass

D=6

D=10

DLp MM 3.1

DLp MM 9.2

DLp MM 9.2

At least three definitions:

Just numerical coefficients

But: there is essential differencebetween M about 1 TeV and 2 TeV for the LHC!


At what energy can we safely speak about true BH prods?At what energy can we safely speak about true BH prods?

Clearly E > MD. But how much large?


Inelasticity in BH Production and XInelasticity in BH Production and Xminmin

Production efficiency curve, for example:

What part of initial collision energy actuallywas trapped in BH formation process?

inelasticity


BH Production in UHECRBH Production in UHECR

n=1-7, 5 Yrs.

Pierre-Auger Observatory


Inelasticity and BH Production at the LHC and at the PAO Inelasticity and BH Production at the LHC and at the PAO

Inelasticity is much more restrictive factorfor the LHC because it is limited in energy by 14 TeV


The discovery reaches for the LHCThe discovery reaches for the LHC

This region excluded by PAO

n=6


Who is “pessimist” ? Pessimist is au fait optimist…

Resume (not hard and final, because too many calculations and theoreticalInvestigation are waiting to be done in this field)

• Black Holes is not a such spectacular signature as commonly advertized earlier (from the very first papers in 1998).

• Likely the LHC will not be able to observe classical thermal BH decays.

• Careful counting pushes the minimal value of BH mass to higher energies what make observation of BH hopeless at the LHC (important moment: there are alternative point of views on this problem, not just one possible).

• In any case for TeV scale gravity near the threshold we will see signatures of QG (if one of them are realized by Nature). • We can’t calculate its and make quantitative prediction. But these signatures can be distinguished from other possible new physics (by high transversality for final states). Futher experimental technics?

m.savina, november 25, npd ras 2009 1 black hole production at the lhc: peculiarities, problems,...

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