ОТЧЕТ ИЯИ РАН за 2007 год

Участвует 16 сотрудников

ОСНОВНОЕ НАПРАВЛЕНИЕ ИССЛЕДОВАНИЙ – построение моделей за рамками СМ, феноменологический анализ процессов при энергии коллайдера LHC, полное моделирование отклика детектора CMS

ОСНОВНЫЕ РЕЗУЛЬТАТЫ

Выполнен полный расчет с учетом отклика детектора CMS по следующим темам:

• эксклюзивное рождение слептонов для сигнатуры l+l- + ET

miss + no jets

• поиск суперсимметрии и нарушения лептонного флейворного числа на основе сигнатуры e± + ET

miss

• поиск правого заряженного калибровочного бозона и тяжелого нейтрино на основе сигнатуры e+e- + 2 jets

Разработано программное обеспечение для статистической обработки данных эксперимента CMS

ОСНОВНЫЕ РЕЗУЛЬТАТЫ (II)

Эти результаты вошли в CMS Physics Technical Design Report Vol.II Physics Performance. Группой ИЯИ РАН по этим темам опубликовано три CMS Analysis Notes (из 60, составивших основу PhTDR). Доля группы ИЯИ РАН составила 5%.

Группа ИЯИ РАН внесла основной вклад в готовящийся в ЦЕРНе отчет о результатах рабочей встречи “Flavour in the LHC Epoch”

НЕКОТОРЫЕ ПУБЛИКАЦИИ

• CMS Collaboration (Austin Ball et al.). CMS technical design report, volume II: Physics performance. J.Phys.G34:995-1579,2007.

• Yu.M. Andreev, S.I. Bityukov, N.V. Krasnikov, A.N. Toropin. Using the e+- mu-+ + E**miss(T) signature in the search for supersymmetry and lepton flavour violation in neutralino decays. Phys.Atom.Nucl.70:1717-1724,2007.

• S.N. Gninenko, M.M. Kirsanov, N.V. Krasnikov, V.A. Matveev. Detection of heavy Majorana neutrinos and right-handed bosons. Phys.Atom.Nucl.70:441-449,2007.

• N.V. Krasnikov. Unparticle as a field with continuously distributed mass. Int.J.Mod.Phys. A22: 5117, 2007.

• N.V. Krasnikov et al. Searching for energetic cosmic axions in a laboratory experiment: Testing the PVLAS anomaly. Eur.Phys.J. C52: 899-904, 2007.

• S.N. Gninenko, N.V. Krasnikov, A. Rubbia. Search for millicharged particles in reactor neutrino experiments: A Probe of the PVLAS anomaly. Phys.Rev.D75:075014,2007.  

НЕКОТОРЫЕ ДОКЛАДЫ

• N.V.Krasnikov, V.A.Matveev. Search for new physics at LHC. Proceedings XIII Lomonosov conference on elementary particle physics, Moscow, Russia, 23-30 August, 2007.

Отчет НИИЯФ МГУ за 2007 годОтчет НИИЯФ МГУ за 2007 годУчаствует 11 сотрудников ОТФВЭ

Основные направления исследований

1. Построение моделей за рамками СМ, расчеты и феноменологический анализ процессов при энергиях коллайдеров Tevatron, LHC, ILC Некоторые результаты - первое наблюдение одиночного рождения топ-кварка в экпарименте D0 c использованием генератора SingleTop (CompHEP) для моделирования сигнала - исследованы перспективы поика одиночного топ-кварка на LHC, поиск на его основе W'-бозона, FCNC, anom.Wtb - проведен анализ возможностей поиска KK-состояний в стабилизированной RS модели,

перспективы поиска под порогом рождения KK-состояний - исследованы возможности поика бозона Хиггса в сценариях а явных CP нарушением

2. Автоматизация вычислений и генерации событий Некоторые результаты - создана новая версия программы CompHEP с новым стандартом записи событий - реализована новая версия генератора SingleTop на базе CompHEP с включением FCNC и WTb anomalous couplings

V.M.Abazov,..., E.E.Boos, ..., V.E.Bunichev,...L.V.Dudko... et al. [D0Collaboration],

Evidence for production of single top quarks and first direct measurement of |V(tb)|, Phys. Rev. Lett. 98 (2007) 181802

G.~L.~Bayatian et al. [CMS Collaboration], CMS technical design report, volume II: Physics performance, J. Phys. G 34 (2007) 995.

E.Boos, V.Bunichev, L.Dudko and M.Perfilov, Interference between W' and W in single-top quark production processes, Phys. Lett. B 655 (2007) 245

E.Akhmetzyanova, M.Dolgopolov, M.Dubinin Supersymmetric threshold corrections to the Higgs sector in the MSSM featuring explicit CP violation, Ядерная физика, т.70, вып.9, с.1549 (2007)

E.E.Boos, V.E.Bunichev, M.N.Smolyakov and I.P.Volobuev, Testing extra dimensions below the production threshold of Kaluza-Klein excitations,'' Preprint: arXiv:0710.3100 [hep-ph]

E.~Boos, V.~Bunichev and H.~J.~Schreiber, Prospects of a Search for a New Massless Neutral Gauge Boson at the ILC, Preprint arXiv:0709.4535 [hep-ph]

J.Alwall, E.Boos, ..., L.Dudko, ..., A.Sherstnev et al. А standard format for Les Houches event files Comput. Phys. Commun. 176 (2007) 300

Некоторые публикации

CompHEP (НИИЯФ МГУ): CompHEP (НИИЯФ МГУ):

Автоматические символьные и численные вычисления Автоматические символьные и численные вычисления

от задания Лагранжиана до моделирования событийот задания Лагранжиана до моделирования событий

Программа в свободном доступе Программа в свободном доступе http://comphep.sinp.msu.ruhttp://comphep.sinp.msu.ru

CompHEP – инструмент теоретических CompHEP – инструмент теоретических исследований в физике высоких энергийисследований в физике высоких энергий

CompHEP коллаборация: Э.Боос, В.Буничев, М.Дубинин, Л.Дудко, В.Еднерал, В.Ильин, А.Крюков, В.Саврин, А.Семенов, А.Шерстнев

Встроенные модели:Стандартная модельМССМЛептокварки, W’, аномальные Wtb и FCNC вершиныМодели с дополнительными измерениями

…….

Single Top QuarkFirst evidence for Single top production

at Fermilab in 2007

Active participation of SINP MSUphysicists in the D0 analysis. D0 ExperienceD0 Experience CMS AnalysisCMS Analysis

Generator SingleTop (based on CompHEP) for the signal

CMS Single Top Search

PTDR v.II (Cut based analysis)

Improved by Neural Network (CMS-IN-2007/045)

1fb-1: Evidence

10fb-1: Discovery; |Vtb|, Mtop; W', FCNC,

anomalous Wtb

RDMS Team (part of the international single top group) SINP MSU: E.Boos, V.Bunichev, L.Dudko, A.Markina, V.Savrin IHEP: V.Abramov, A.Ashimova, D.Konstantinov, S.Slabospitsky

Introduction

Large Hadron Collider (LHC) Start: 2008Two proton beams with total energy E = 14 TeVLow luminosity stage with Llow = 1033 cm-2s-1 Remember: Nev = sigma Ltwith total luminosity Lt = 10 fb-1 per year Remember: 1 fb = 10-39 cm2s-1

Two big detectors:CMS (Compact Muon Solenoid)ATLAS (A Toroidal LHC ApparatuS)

In this talk we review the search for supersymmetry

Total weight 7000 tOverall diameter 25 mBarrel toroid length 26 mEnd-cap end-wall chamber span 46 mMagnetic field 2 Tesla

Total weight 12 500 tOverall diameter 15.00 mOverall length 21.6 mMagnetic field 4 Tesla

Total weight 12 500 tOverall diameter 15.00 mOverall length 21.6 mMagnetic field 4 TeslaDetector subsystems are designed to measure:

energy and momentum of ,e, , jets, missing ET up to a few TeV

ATLAS and CMS ExperimentsLarge general-purpose particle physics detectors

Compact Muon SolenoidA Large Toroidal LHC ApparatuS

Search for Supersymmetry Y.A.Goldman and E.P.Likhtman

D.V.Volkov and V.P.Akulov

J.Wess and B.Zumino

Why we like SUSY?• elegant theory• technical solution of the gauge hierarchy

problem• dark matter LSP is natural candidate• consistent string theories are superstring

theories

SUSY, Rules of the GameMSSM – minimal supersymmetric standard model

based on gauge

group. For each known particle superanalog

superparticle (the same mass and internal quantum numbers, difference only in spin)

g (gluon, s = 1) (gluino , s = ½)

quarks (s = ½) squarks (s = 0)

leptons (s = ½) sleptons (s = 0)

gauge bosons (photon, Z- and W-bosons) (s =1)

gaugino (s = ½)

(3) (2) (1)c LSU SU U

g

SUSY, Rules of the Game H1, H2 (two Higgs doublets) (s = 0)

Higgsino (s =1/2)

As a result of gaugino and higgsino mixing

in mass spectrum:

two chargino (s = ½)

four neutralino (s = ½ )

R-parity conservation postulate to get

rid of dangerous terms leading to fast proton decay.

For ordinary particles R = +1

1 2,

0 0 0 01 2 3 4, , ,

SUSY, Rules of the Game

For sparticles R = -1 R-parity is conserved by construction Two important consequences: 1. At supercolliders sparticles are pair

produced 2. The lightest sparticle (LSP) is stable:

dark matter candidate

• Note that SUSY models with R-parity violation are possible

01

mSUGRA Model

So SUSY has to be broken and in general

masses of sparticles (squarks, sleptons, gluino, gaugino, higgsino) are arbitrary

that makes analysis extremely difficult.

For LHC most calculations were done

within so called mSUGRA model squark, slepton, higgsino masses are

universal at GUT scale m0

Gaugino masses also universal m1/2

Sparticle ProductionFrom cosmology and astrophysics

LSP is weakly interacting neutral particle.

As a result LSP escapes from detection

(analog of neutrino) SUSY events are characterized by nonzero transverse

missing momentum.

In real life SUSY has to be broken

1. gravity mediated SUSY breaking

2. gauge mediated SUSY breaking

Sparticle Production

At LHC sparticles can be produced via reactions:

For squarks and gluino with masses O(1) TeV squark and gluino cross sections O(1) pb

, , , ,gg qq qg gg qg qq

0 0, , , ,i i i iqq qg g g q q

0 0 0, ,i j i j i jqq

, ,qq l ll

The Total SUSY Cross Sections

LHC SUSY SearchesTypical Signature/decay chain:

• Strongly interacting sparticles (squarks, gluinos) dominate production.

• Heavier than sleptons, gauginos etc. g cascade decays to LSP.

• Potentially long decay chains and large mass differences

– Many high pT objects observed (leptons, jets, b-jets).

• If R-Parity conserved LSP (lightest neutralino in mSUGRA) stable and sparticles pair produced.

– Large ETmiss signature (c.f. Wgl).

SUSY Searches• Inclusive searches to detect SUSY with first data• Exclusive studies – performed with more data to determine model parameters e.g. masses etc from end point measurements…

lqql

g~ q~ l~

~

~p p

~

SUSY Signatures As a result of squark, gluino decays and

chargino and neutralino decays, the most

interesting signatures for the search for

SUSY at LHC are:

• multijets plus ETmiss events

• 1l plus jets plus ETmiss events

• 2l plus jets plus ETmiss events

• 3l plus jets plus ETmiss events

• 4l plus jets plus ETmiss events

Recent CMS Full Simulation Results

SUSY signatures:

1. EmissT + (n > 2) jets

For tan(beta) =10, m0 = 60 GeV, m1/2=250 GeV, sign(mu) = +1

the 5 sigma discovery is for Lt=2 pb-1 first 4 hours of LHC work !!!

2. The same sign dimuons + EmissT + (n>2) jets

For Lt =10 fb-1 SUSY masses up to 1.5 TeV

CMS SUSY Discovery Potential

Recent CMS Full Simulation Results

3. Single muon + EmissT + (n>2) jets

For Lt = 100 fb-1 5 sigma discovery for

SUSY masses up to 2TeV.

4. Opposite sign leptons + EmissT + (n>2) jets

Basically similar to signature with single muon

Dilepton Invariant Mass Distributionfor the Test Point LM1

LHC SUSY Discovery Potential• The main conclusion is that for mSUGRA

model LHC will be able to discover SUSY

with squark and gluino masses up to

2 .5 TeV for Ltot = 100 fb-1

• Chargino and neutralino pairs produced through DY mechanism may be

detected through their leptonic decays

The signature: 3 isolated leptons without jet activity. LHC is able to detect such DY production with masses up to 200 GeV

01 2pp

01 2

missTlll E

Determination of Sparticle Masses

In many cases LHC is able not only to discover SUSY but to determine SUSY breaking parameters (combinations of sparticle masses). For instance, using l+ l- invariant mass distribution in reaction

it is possible to determine the combination

as endpoint in edge structure with the accuracy of 2-3%

0 02 1 l l

0 02 1

M M

Conclusions CMS & ATLAS have significant discovery

potential LHC will be able to discover SUSY with squark and gluino masses up to 2.5 TeV. There is nonzero probability to find something beyond SM or MSSM(extra dimensions, Z’-boson, compositeness ...) Heavy gauge bosons up to ~5-6 TeV Heavy neutrino up to 2.6 TeV RS model ED up to ~4 TeV

Conclusions

At any rate after LHC we will know the mechanism of electroweak symmetry breaking (Higgs boson or something more

exotic?) and the basic properties of the

matter structure at TeV scale.